Member Function Documentation

QString::QString()

Constructs a null string. Null strings are also empty.

See also isEmpty().

QString::QString(const QChar *unicode, int size = -1)

Constructs a string initialized with the first size characters of the QChar array unicode.

If unicode is 0, a null string is constructed.

If size is negative, unicode is assumed to point to a nul-terminated array and its length is determined dynamically. The terminating nul-character is not considered part of the string.

QString makes a deep copy of the string data. The unicode data is copied as is and the Byte Order Mark is preserved if present.

See also fromRawData().

QString::QString(QChar ch)

Constructs a string of size 1 containing the character ch.

QString::QString(int size, QChar ch)

Constructs a string of the given size with every character set to ch.

See also fill().

QString::QString(QLatin1String str)

Constructs a copy of the Latin-1 string str.

See also fromLatin1().

QString::QString(const QString &other)

Constructs a copy of other.

This operation takes constant time, because QString is implicitly shared. This makes returning a QString from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time.

See also operator=().

QString::QString(QString &&other)

Move-constructs a QString instance, making it point at the same object that other was pointing to.

This function was introduced in Qt 5.2.

QString::QString(const char *str)

Constructs a string initialized with the 8-bit string str. The given const char pointer is converted to Unicode using the fromUtf8() function.

You can disable this constructor by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

Note: Defining QT_RESTRICTED_CAST_FROM_ASCII also disables this constructor, but enables a QString(const char (&ch)[N]) constructor instead. Using non-literal input, or input with embedded NUL characters, or non-7-bit characters is undefined in this case.

See also fromLatin1(), fromLocal8Bit(), and fromUtf8().

QString::QString(const QByteArray &ba)

Constructs a string initialized with the byte array ba. The given byte array is converted to Unicode using fromUtf8(). Stops copying at the first 0 character, otherwise copies the entire byte array.

You can disable this constructor by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

See also fromLatin1(), fromLocal8Bit(), and fromUtf8().

QString::~QString()

Destroys the string.

QString &QString::append(const QString &str)

Appends the string str onto the end of this string.

Example:

QString x = "free";
QString y = "dom";

x.append(y);
// x == "freedom"

This is the same as using the insert() function:

x.insert(x.size(), y);

The append() function is typically very fast (constant time), because QString preallocates extra space at the end of the string data so it can grow without reallocating the entire string each time.

See also operator+=(), prepend(), and insert().

QString &QString::append(const QChar *str, int len)

This function overloads append().

Appends len characters from the QChar array str to this string.

This function was introduced in Qt 5.0.

QString &QString::append(QChar ch)

This function overloads append().

Appends the character ch to this string.

QString &QString::append(const QStringRef &reference)

Appends the given string reference to this string and returns the result.

This function was introduced in Qt 4.4.

QString &QString::append(QLatin1String str)

This function overloads append().

Appends the Latin-1 string str to this string.

QString &QString::append(const char *str)

This function overloads append().

Appends the string str to this string. The given const char pointer is converted to Unicode using the fromUtf8() function.

You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

QString &QString::append(const QByteArray &ba)

This function overloads append().

Appends the byte array ba to this string. The given byte array is converted to Unicode using the fromUtf8() function.

You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

QString QString::arg(const QString &a, int fieldWidth = 0, QChar fillChar = QLatin1Char( ' ' )) const

Returns a copy of this string with the lowest numbered place marker replaced by string a, i.e., %1, %2, ..., %99.

fieldWidth specifies the minimum amount of space that argument a shall occupy. If a requires less space than fieldWidth, it is padded to fieldWidth with character fillChar. A positive fieldWidth produces right-aligned text. A negative fieldWidth produces left-aligned text.

This example shows how we might create a status string for reporting progress while processing a list of files:

QString i;           // current file's number
QString total;       // number of files to process
QString fileName;    // current file's name

QString status = QString("Processing file %1 of %2: %3")
                .arg(i).arg(total).arg(fileName);

First, arg(i) replaces %1. Then arg(total) replaces %2. Finally, arg(fileName) replaces %3.

One advantage of using arg() over asprintf() is that the order of the numbered place markers can change, if the application's strings are translated into other languages, but each arg() will still replace the lowest numbered unreplaced place marker, no matter where it appears. Also, if place marker %i appears more than once in the string, the arg() replaces all of them.

If there is no unreplaced place marker remaining, a warning message is output and the result is undefined. Place marker numbers must be in the range 1 to 99.

QString QString::arg(qulonglong a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a into a string. base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(long a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The a argument is expressed in the given base, which is 10 by default and must be between 2 and 36.

The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale. The default locale is determined from the system's locale settings at application startup. It can be changed using QLocale::setDefault(). The 'L' flag is ignored if base is not 10.

QString str;
str = QString("Decimal 63 is %1 in hexadecimal")
        .arg(63, 0, 16);
// str == "Decimal 63 is 3f in hexadecimal"

QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
str = QString("%1 %L2 %L3")
        .arg(12345)
        .arg(12345)
        .arg(12345, 0, 16);
// str == "12345 12,345 3039"

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(ulong a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a to a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

The a argument is expressed in base base, which is 10 by default and must be between 2 and 36. For bases other than 10, a is treated as an unsigned integer.

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale::setDefault(). If no default locale was specified, the "C" locale is used. The 'L' flag is ignored if base is not 10.

QString str;
str = QString("Decimal 63 is %1 in hexadecimal")
        .arg(63, 0, 16);
// str == "Decimal 63 is 3f in hexadecimal"

QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
str = QString("%1 %L2 %L3")
        .arg(12345)
        .arg(12345)
        .arg(12345, 0, 16);
// str == "12345 12,345 3039"

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(uint a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(short a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(ushort a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(double a, int fieldWidth = 0, char format = 'g', int precision = -1, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

Argument a is formatted according to the specified format and precision. See Argument Formats for details.

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

double d = 12.34;
QString str = QString("delta: %1").arg(d, 0, 'E', 3);
// str == "delta: 1.234E+01"

The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale::setDefault(). If no default locale was specified, the "C" locale is used.

If fillChar is '0' (the number 0, ASCII 48), this function will use the locale's zero to pad. For negative numbers, the zero padding will probably appear before the minus sign.

See also QLocale::toString().

QString QString::arg(char a, int fieldWidth = 0, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

The a argument is interpreted as a Latin-1 character.

QString QString::arg(QChar a, int fieldWidth = 0, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

QString QString::arg(qlonglong a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char( ' ' )) const

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString::arg(const QString &a1, const QString &a2) const

This function overloads arg().

This is the same as str.arg(a1).arg(a2), except that the strings a1 and a2 are replaced in one pass. This can make a difference if a1 contains e.g. %1:

QString str;
str = "%1 %2";

str.arg("%1f", "Hello");        // returns "%1f Hello"
str.arg("%1f").arg("Hello");    // returns "Hellof %2"

A similar problem occurs when the numbered place markers are not white space separated:

QString str;
str = "%1%3%2";
str.arg("Hello").arg(20).arg(50); // returns "Hello500"

str = "%1%2%3";
str.arg("Hello").arg(50).arg(20); // returns "Hello5020"

Let's look at the substitutions:

• First, Hello replaces %1 so the string becomes "Hello%3%2".
• Then, 20 replaces %2 so the string becomes "Hello%320".
• Since the maximum numbered place marker value is 99, 50 replaces %32.

Thus the string finally becomes "Hello500".

In such cases, the following yields the expected results:

QString str;
str = "%1%2%3";
str.arg("Hello", QString::number(20), QString::number(50)); // returns "Hello5020"

QString QString::arg(const QString &a1, const QString &a2, const QString &a3) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3), except that the strings a1, a2 and a3 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4), except that the strings a1, a2, a3 and a4 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4, const QString &a5) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5), except that the strings a1, a2, a3, a4, and a5 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4, const QString &a5, const QString &a6) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6)), except that the strings a1, a2, a3, a4, a5, and a6 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4, const QString &a5, const QString &a6, const QString &a7) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7), except that the strings a1, a2, a3, a4, a5, a6, and a7 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4, const QString &a5, const QString &a6, const QString &a7, const QString &a8) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8), except that the strings a1, a2, a3, a4, a5, a6, a7, and a8 are replaced in one pass.

QString QString::arg(const QString &a1, const QString &a2, const QString &a3, const QString &a4, const QString &a5, const QString &a6, const QString &a7, const QString &a8, const QString &a9) const

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8).arg(a9), except that the strings a1, a2, a3, a4, a5, a6, a7, a8, and a9 are replaced in one pass.

[static] QString QString::asprintf(const char *cformat, ...)

Safely builds a formatted string from the format string cformat and an arbitrary list of arguments.

The format string supports the conversion specifiers, length modifiers, and flags provided by printf() in the standard C++ library. The cformat string and %s arguments must be UTF-8 encoded.

Note: The %lc escape sequence expects a unicode character of type char16_t, or ushort (as returned by QChar::unicode()). The %ls escape sequence expects a pointer to a zero-terminated array of unicode characters of type char16_t, or ushort (as returned by QString::utf16()). This is at odds with the printf() in the standard C++ library, which defines %lc to print a wchar_t and %ls to print a wchar_t*, and might also produce compiler warnings on platforms where the size of wchar_t is not 16 bits.

Warning: We do not recommend using QString::asprintf() in new Qt code. Instead, consider using QTextStream or arg(), both of which support Unicode strings seamlessly and are type-safe. Here's an example that uses QTextStream:

QString result;
QTextStream(&result) << "pi = " << 3.14;
// result == "pi = 3.14"

For translations, especially if the strings contains more than one escape sequence, you should consider using the arg() function instead. This allows the order of the replacements to be controlled by the translator.

This function was introduced in Qt 5.5.

See also arg().

const QChar QString::at(int position) const

Returns the character at the given index position in the string.

The position must be a valid index position in the string (i.e., 0 <= position < size()).

See also operator[]().

iterator QString::begin()

Returns an STL-style iterator pointing to the first character in the string.

See also constBegin() and end().

const_iterator QString::begin() const

This function overloads begin().

int QString::capacity() const

Returns the maximum number of characters that can be stored in the string without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to know how many characters are in the string, call size().

See also reserve() and squeeze().

const_iterator QString::cbegin() const

Returns a const STL-style iterator pointing to the first character in the string.

This function was introduced in Qt 5.0.

See also begin() and cend().

const_iterator QString::cend() const

Returns a const STL-style iterator pointing to the imaginary character after the last character in the list.

This function was introduced in Qt 5.0.

See also cbegin() and end().

void QString::chop(int n)

Removes n characters from the end of the string.

If n is greater than or equal to size(), the result is an empty string; if n is negative, it is equivalent to passing zero.

Example:

QString str("LOGOUT\r\n");
str.chop(2);
// str == "LOGOUT"

If you want to remove characters from the beginning of the string, use remove() instead.

See also truncate(), resize(), remove(), and QStringRef::chop().

void QString::clear()

Clears the contents of the string and makes it null.

See also resize() and isNull().

[static] int QString::compare(const QString &s1, const QString &s2, Qt::CaseSensitivity cs = Qt::CaseSensitive)

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

If cs is Qt::CaseSensitive, the comparison is case sensitive; otherwise the comparison is case insensitive.

Case sensitive comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-visible strings with localeAwareCompare().

int x = QString::compare("aUtO", "AuTo", Qt::CaseInsensitive);  // x == 0
int y = QString::compare("auto", "Car", Qt::CaseSensitive);     // y > 0
int z = QString::compare("auto", "Car", Qt::CaseInsensitive);   // z < 0

This function was introduced in Qt 4.2.

See also operator==(), operator<(), and operator>().

int QString::compare(QLatin1String other, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads compare().

Same as compare(*this, other, cs).

This function was introduced in Qt 4.2.

int QString::compare(const QString &other, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads compare().

Lexically compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

Same as compare(*this, other, cs).

This function was introduced in Qt 4.2.

[static] int QString::compare(const QString &s1, QLatin1String s2, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads compare().

Performs a comparison of s1 and s2, using the case sensitivity setting cs.

This function was introduced in Qt 4.2.

[static] int QString::compare(QLatin1String s1, const QString &s2, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads compare().

Performs a comparison of s1 and s2, using the case sensitivity setting cs.

This function was introduced in Qt 4.2.

int QString::compare(const QStringRef &ref, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads compare().

Compares the string reference, ref, with the string and returns an integer less than, equal to, or greater than zero if the string is less than, equal to, or greater than ref.

[static] int QString::compare(const QString &s1, const QStringRef &s2, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads compare().

const_iterator QString::constBegin() const

Returns a const STL-style iterator pointing to the first character in the string.

See also begin() and constEnd().

const QChar *QString::constData() const

Returns a pointer to the data stored in the QString. The pointer can be used to access the characters that compose the string. For convenience, the data is '\0'-terminated.

Note that the pointer remains valid only as long as the string is not modified.

See also data() and operator[]().

const_iterator QString::constEnd() const

Returns a const STL-style iterator pointing to the imaginary character after the last character in the list.

See also constBegin() and end().

bool QString::contains(const QString &str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns true if this string contains an occurrence of the string str; otherwise returns false.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString str = "Peter Pan";
str.contains("peter", Qt::CaseInsensitive);    // returns true

See also indexOf() and count().

bool QString::contains(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads contains().

Returns true if this string contains an occurrence of the character ch; otherwise returns false.

bool QString::contains(QLatin1String str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads contains().

Returns true if this string contains an occurrence of the latin-1 string str; otherwise returns false.

This function was introduced in Qt 5.3.

bool QString::contains(const QStringRef &str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns true if this string contains an occurrence of the string reference str; otherwise returns false.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also indexOf() and count().

bool QString::contains(const QRegExp &rx) const

This function overloads contains().

Returns true if the regular expression rx matches somewhere in this string; otherwise returns false.

bool QString::contains(QRegExp &rx) const

This function overloads contains().

Returns true if the regular expression rx matches somewhere in this string; otherwise returns false.

If there is a match, the rx regular expression will contain the matched captures (see QRegExp::matchedLength, QRegExp::cap).

This function was introduced in Qt 4.5.

bool QString::contains(const QRegularExpression &re) const

This function overloads contains().

Returns true if the regular expression re matches somewhere in this string; otherwise returns false.

This function was introduced in Qt 5.0.

bool QString::contains(const QRegularExpression &re, QRegularExpressionMatch *match) const

This function overloads contains().

Returns true if the regular expression re matches somewhere in this string; otherwise returns false.

If the match is successful and match is not a null pointer, it also writes the results of the match into the QRegularExpressionMatch object pointed to by match.

This function was introduced in Qt 5.1.

See also QRegularExpression::match().

int QString::count(const QString &str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns the number of (potentially overlapping) occurrences of the string str in this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

See also contains() and indexOf().

int QString::count(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads count().

Returns the number of occurrences of character ch in the string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

See also contains() and indexOf().

int QString::count() const

This function overloads count().

Same as size().

int QString::count(const QStringRef &str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads count().

Returns the number of (potentially overlapping) occurrences of the string reference str in this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also contains() and indexOf().

int QString::count(const QRegExp &rx) const

This function overloads count().

Returns the number of times the regular expression rx matches in the string.

This function counts overlapping matches, so in the example below, there are four instances of "ana" or "ama":

QString str = "banana and panama";
str.count(QRegExp("a[nm]a"));    // returns 4

int QString::count(const QRegularExpression &re) const

This function overloads count().

Returns the number of times the regular expression re matches in the string.

This function counts overlapping matches, so in the example below, there are four instances of "ana" or "ama":

QString str = "banana and panama";
str.count(QRegularExpression("a[nm]a"));    // returns 4

This function was introduced in Qt 5.0.

const_reverse_iterator QString::crbegin() const

Returns a const STL-style reverse iterator pointing to the first character in the string, in reverse order.

This function was introduced in Qt 5.6.

See also begin(), rbegin(), and rend().

const_reverse_iterator QString::crend() const

Returns a const STL-style reverse iterator pointing to one past the last character in the string, in reverse order.

This function was introduced in Qt 5.6.

See also end(), rend(), and rbegin().

QChar *QString::data()

Returns a pointer to the data stored in the QString. The pointer can be used to access and modify the characters that compose the string. For convenience, the data is '\0'-terminated.

Example:

QString str = "Hello world";
QChar *data = str.data();
while (!data->isNull()) {
    qDebug() << data->unicode();
    ++data;
}

Note that the pointer remains valid only as long as the string is not modified by other means. For read-only access, constData() is faster because it never causes a deep copy to occur.

See also constData() and operator[]().

const QChar *QString::data() const

This is an overloaded function.

iterator QString::end()

Returns an STL-style iterator pointing to the imaginary character after the last character in the string.

See also begin() and constEnd().

const_iterator QString::end() const

This function overloads end().

bool QString::endsWith(const QString &s, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns true if the string ends with s; otherwise returns false.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

QString str = "Bananas";
str.endsWith("anas");         // returns true
str.endsWith("pple");         // returns false

See also startsWith().

bool QString::endsWith(const QStringRef &s, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads endsWith().

Returns true if the string ends with the string reference s; otherwise returns false.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also startsWith().

bool QString::endsWith(QLatin1String s, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads endsWith().

bool QString::endsWith(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns true if the string ends with c; otherwise returns false.

This function overloads endsWith().

QString &QString::fill(QChar ch, int size = -1)

Sets every character in the string to character ch. If size is different from -1 (default), the string is resized to size beforehand.

Example:

QString str = "Berlin";
str.fill('z');
// str == "zzzzzz"

str.fill('A', 2);
// str == "AA"

See also resize().

[static] QString QString::fromCFString(CFStringRef string)

Constructs a new QString containing a copy of the string CFString.

Note: this function is only available on OS X and iOS.

This function was introduced in Qt 5.2.

[static] QString QString::fromLatin1(const char *str, int size = -1)

Returns a QString initialized with the first size characters of the Latin-1 string str.

If size is -1 (default), it is taken to be strlen(str).

See also toLatin1(), fromUtf8(), and fromLocal8Bit().

[static] QString QString::fromLatin1(const QByteArray &str)

This is an overloaded function.

Returns a QString initialized with the Latin-1 string str.

This function was introduced in Qt 5.0.

[static] QString QString::fromLocal8Bit(const char *str, int size = -1)

Returns a QString initialized with the first size characters of the 8-bit string str.

If size is -1 (default), it is taken to be strlen(str).

QTextCodec::codecForLocale() is used to perform the conversion.

See also toLocal8Bit(), fromLatin1(), and fromUtf8().

[static] QString QString::fromLocal8Bit(const QByteArray &str)

This is an overloaded function.

Returns a QString initialized with the 8-bit string str.

This function was introduced in Qt 5.0.

[static] QString QString::fromNSString(const NSString *string)

Constructs a new QString containing a copy of the string NSString.

Note: this function is only available on OS X and iOS.

This function was introduced in Qt 5.2.

[static] QString QString::fromRawData(const QChar *unicode, int size)

Constructs a QString that uses the first size Unicode characters in the array unicode. The data in unicode is not copied. The caller must be able to guarantee that unicode will not be deleted or modified as long as the QString (or an unmodified copy of it) exists.

Any attempts to modify the QString or copies of it will cause it to create a deep copy of the data, ensuring that the raw data isn't modified.

Here's an example of how we can use a QRegExp on raw data in memory without requiring to copy the data into a QString:

QRegExp pattern;
static const QChar unicode[] = {
        0x005A, 0x007F, 0x00A4, 0x0060,
        0x1009, 0x0020, 0x0020};
int size = sizeof(unicode) / sizeof(QChar);

QString str = QString::fromRawData(unicode, size);
if (str.contains(QRegExp(pattern))) {
    // ...
}

Warning: A string created with fromRawData() is not '\0'-terminated, unless the raw data contains a '\0' character at position size. This means unicode() will not return a '\0'-terminated string (although utf16() does, at the cost of copying the raw data).

See also fromUtf16() and setRawData().

[static] QString QString::fromStdString(const std::string &str)

Returns a copy of the str string. The given string is converted to Unicode using the fromUtf8() function.

See also fromLatin1(), fromLocal8Bit(), fromUtf8(), and QByteArray::fromStdString().

[static] QString QString::fromStdU16String(const std::u16string &str)

Returns a copy of the str string. The given string is assumed to be encoded in UTF-16.

This function was introduced in Qt 5.5.

See also fromUtf16(), fromStdWString(), and fromStdU32String().

[static] QString QString::fromStdU32String(const std::u32string &str)

Returns a copy of the str string. The given string is assumed to be encoded in UCS-4.

This function was introduced in Qt 5.5.

See also fromUcs4(), fromStdWString(), and fromStdU16String().

[static] QString QString::fromStdWString(const std::wstring &str)

Returns a copy of the str string. The given string is assumed to be encoded in utf16 if the size of wchar_t is 2 bytes (e.g. on windows) and ucs4 if the size of wchar_t is 4 bytes (most Unix systems).

See also fromUtf16(), fromLatin1(), fromLocal8Bit(), fromUtf8(), fromUcs4(), fromStdU16String(), and fromStdU32String().

[static] QString QString::fromUcs4(const uint *unicode, int size = -1)

Returns a QString initialized with the first size characters of the Unicode string unicode (ISO-10646-UCS-4 encoded).

If size is -1 (default), unicode must be terminated with a 0.

This function was introduced in Qt 4.2.

See also toUcs4(), fromUtf16(), utf16(), setUtf16(), fromWCharArray(), and fromStdU32String().

[static] QString QString::fromUcs4(const char32_t *str, int size = -1)

Returns a QString initialized with the first size characters of the Unicode string str (ISO-10646-UCS-4 encoded).

If size is -1 (default), str must be terminated with a 0.

This function was introduced in Qt 5.3.

See also toUcs4(), fromUtf16(), utf16(), setUtf16(), fromWCharArray(), and fromStdU32String().

[static] QString QString::fromUtf8(const char *str, int size = -1)

Returns a QString initialized with the first size bytes of the UTF-8 string str.

If size is -1 (default), it is taken to be strlen(str).

UTF-8 is a Unicode codec and can represent all characters in a Unicode string like QString. However, invalid sequences are possible with UTF-8 and, if any such are found, they will be replaced with one or more "replacement characters", or suppressed. These include non-Unicode sequences, non-characters, overlong sequences or surrogate codepoints encoded into UTF-8.

This function can be used to process incoming data incrementally as long as all UTF-8 characters are terminated within the incoming data. Any unterminated characters at the end of the string will be replaced or suppressed. In order to do stateful decoding, please use QTextDecoder.

See also toUtf8(), fromLatin1(), and fromLocal8Bit().

[static] QString QString::fromUtf8(const QByteArray &str)

This is an overloaded function.

Returns a QString initialized with the UTF-8 string str.

This function was introduced in Qt 5.0.

[static] QString QString::fromUtf16(const ushort *unicode, int size = -1)

Returns a QString initialized with the first size characters of the Unicode string unicode (ISO-10646-UTF-16 encoded).

If size is -1 (default), unicode must be terminated with a 0.

This function checks for a Byte Order Mark (BOM). If it is missing, host byte order is assumed.

This function is slow compared to the other Unicode conversions. Use QString(const QChar *, int) or QString(const QChar *) if possible.

QString makes a deep copy of the Unicode data.

See also utf16(), setUtf16(), and fromStdU16String().

[static] QString QString::fromUtf16(const char16_t *str, int size = -1)

Returns a QString initialized with the first size characters of the Unicode string str (ISO-10646-UTF-16 encoded).

If size is -1 (default), str must be terminated with a 0.

This function checks for a Byte Order Mark (BOM). If it is missing, host byte order is assumed.

This function is slow compared to the other Unicode conversions. Use QString(const QChar *, int) or QString(const QChar *) if possible.

QString makes a deep copy of the Unicode data.

This function was introduced in Qt 5.3.

See also utf16(), setUtf16(), and fromStdU16String().

[static] QString QString::fromWCharArray(const wchar_t *string, int size = -1)

Returns a copy of the string, where the encoding of string depends on the size of wchar. If wchar is 4 bytes, the string is interpreted as UCS-4, if wchar is 2 bytes it is interpreted as UTF-16.

If size is -1 (default), the string has to be 0 terminated.

This function was introduced in Qt 4.2.

See also fromUtf16(), fromLatin1(), fromLocal8Bit(), fromUtf8(), fromUcs4(), and fromStdWString().

int QString::indexOf(const QString &str, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString x = "sticky question";
QString y = "sti";
x.indexOf(y);               // returns 0
x.indexOf(y, 1);            // returns 10
x.indexOf(y, 10);           // returns 10
x.indexOf(y, 11);           // returns -1

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

See also lastIndexOf(), contains(), and count().

int QString::indexOf(QChar ch, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads indexOf().

Returns the index position of the first occurrence of the character ch in the string, searching forward from index position from. Returns -1 if ch could not be found.

int QString::indexOf(QLatin1String str, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString x = "sticky question";
QString y = "sti";
x.indexOf(y);               // returns 0
x.indexOf(y, 1);            // returns 10
x.indexOf(y, 10);           // returns 10
x.indexOf(y, 11);           // returns -1

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

This function was introduced in Qt 4.5.

See also lastIndexOf(), contains(), and count().

int QString::indexOf(const QStringRef &str, int from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads indexOf().

Returns the index position of the first occurrence of the string reference str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

int QString::indexOf(const QRegExp &rx, int from = 0) const

This function overloads indexOf().

Returns the index position of the first match of the regular expression rx in the string, searching forward from index position from. Returns -1 if rx didn't match anywhere.

Example:

QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0);       // returns 4

int QString::indexOf(QRegExp &rx, int from = 0) const

This function overloads indexOf().

Returns the index position of the first match of the regular expression rx in the string, searching forward from index position from. Returns -1 if rx didn't match anywhere.

If there is a match, the rx regular expression will contain the matched captures (see QRegExp::matchedLength, QRegExp::cap).

Example:

QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0);       // returns 4

This function was introduced in Qt 4.5.

int QString::indexOf(const QRegularExpression &re, int from = 0) const

This function overloads indexOf().

Returns the index position of the first match of the regular expression re in the string, searching forward from index position from. Returns -1 if re didn't match anywhere.

Example:

QString str = "the minimum";
str.indexOf(QRegularExpression("m[aeiou]"), 0);       // returns 4

This function was introduced in Qt 5.0.

int QString::indexOf(const QRegularExpression &re, int from, QRegularExpressionMatch *rmatch) const

This is an overloaded function.

Returns the index position of the first match of the regular expression re in the string, searching forward from index position from. Returns -1 if re didn't match anywhere.

If the match is successful and rmatch is not a null pointer, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

Example:

QString str = "the minimum";
QRegularExpressionMatch match;
str.indexOf(QRegularExpression("m[aeiou]"), 0, &match);       // returns 4
// match.captured() == mi

This function was introduced in Qt 5.5.

QString &QString::insert(int position, const QString &str)

Inserts the string str at the given index position and returns a reference to this string.

Example:

QString str = "Meal";
str.insert(1, QString("ontr"));
// str == "Montreal"

If the given position is greater than size(), the array is first extended using resize().

See also append(), prepend(), replace(), and remove().

QString &QString::insert(int position, const QChar *unicode, int size)

This function overloads insert().

Inserts the first size characters of the QChar array unicode at the given index position in the string.

QString &QString::insert(int position, QChar ch)

This function overloads insert().

Inserts ch at the given index position in the string.

QString &QString::insert(int position, const QStringRef &str)

This function overloads insert().

Inserts the string reference str at the given index position and returns a reference to this string.

If the given position is greater than size(), the array is first extended using resize().

This function was introduced in Qt 5.5.

QString &QString::insert(int position, QLatin1String str)

This function overloads insert().

Inserts the Latin-1 string str at the given index position.

QString &QString::insert(int position, const char *str)

This function overloads insert().

Inserts the C string str at the given index position and returns a reference to this string.

If the given position is greater than size(), the array is first extended using resize().

This function is not available when QT_NO_CAST_FROM_ASCII is defined.

This function was introduced in Qt 5.5.

QString &QString::insert(int position, const QByteArray &str)

This function overloads insert().

Inserts the byte array str at the given index position and returns a reference to this string.

If the given position is greater than size(), the array is first extended using resize().

This function is not available when QT_NO_CAST_FROM_ASCII is defined.

This function was introduced in Qt 5.5.

bool QString::isEmpty() const

Returns true if the string has no characters; otherwise returns false.

Example:

QString().isEmpty();            // returns true
QString("").isEmpty();          // returns true
QString("x").isEmpty();         // returns false
QString("abc").isEmpty();       // returns false

See also size().

bool QString::isNull() const

Returns true if this string is null; otherwise returns false.

Example:

QString().isNull();             // returns true
QString("").isNull();           // returns false
QString("abc").isNull();        // returns false

Qt makes a distinction between null strings and empty strings for historical reasons. For most applications, what matters is whether or not a string contains any data, and this can be determined using the isEmpty() function.

See also isEmpty().

bool QString::isRightToLeft() const

Returns true if the string is read right to left.

int QString::lastIndexOf(const QString &str, int from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString x = "crazy azimuths";
QString y = "az";
x.lastIndexOf(y);           // returns 6
x.lastIndexOf(y, 6);        // returns 6
x.lastIndexOf(y, 5);        // returns 2
x.lastIndexOf(y, 1);        // returns -1

See also indexOf(), contains(), and count().

int QString::lastIndexOf(QChar ch, int from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the character ch, searching backward from position from.

int QString::lastIndexOf(QLatin1String str, int from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString x = "crazy azimuths";
QString y = "az";
x.lastIndexOf(y);           // returns 6
x.lastIndexOf(y, 6);        // returns 6
x.lastIndexOf(y, 5);        // returns 2
x.lastIndexOf(y, 1);        // returns -1

This function was introduced in Qt 4.5.

See also indexOf(), contains(), and count().

int QString::lastIndexOf(const QStringRef &str, int from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the string reference str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also indexOf(), contains(), and count().

int QString::lastIndexOf(const QRegExp &rx, int from = -1) const

This function overloads lastIndexOf().

Returns the index position of the last match of the regular expression rx in the string, searching backward from index position from. Returns -1 if rx didn't match anywhere.

Example:

QString str = "the minimum";
str.lastIndexOf(QRegExp("m[aeiou]"));      // returns 8

int QString::lastIndexOf(QRegExp &rx, int from = -1) const

This function overloads lastIndexOf().

Returns the index position of the last match of the regular expression rx in the string, searching backward from index position from. Returns -1 if rx didn't match anywhere.

If there is a match, the rx regular expression will contain the matched captures (see QRegExp::matchedLength, QRegExp::cap).

Example:

QString str = "the minimum";
str.lastIndexOf(QRegExp("m[aeiou]"));      // returns 8

This function was introduced in Qt 4.5.

int QString::lastIndexOf(const QRegularExpression &re, int from = -1) const

This function overloads lastIndexOf().

Returns the index position of the last match of the regular expression re in the string, which starts before the index position from. Returns -1 if re didn't match anywhere.

Example:

QString str = "the minimum";
str.lastIndexOf(QRegularExpression("m[aeiou]"));      // returns 8

This function was introduced in Qt 5.0.

int QString::lastIndexOf(const QRegularExpression &re, int from, QRegularExpressionMatch *rmatch) const

This is an overloaded function.

Returns the index position of the last match of the regular expression re in the string, which starts before the index position from. Returns -1 if re didn't match anywhere.

If the match is successful and rmatch is not a null pointer, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

Example:

QString str = "the minimum";
QRegularExpressionMatch match;
str.lastIndexOf(QRegularExpression("m[aeiou]"), -1, &match);      // returns 8
// match.captured() == mu

This function was introduced in Qt 5.5.

QString QString::left(int n) const

Returns a substring that contains the n leftmost characters of the string.

The entire string is returned if n is greater than or equal to size(), or less than zero.

QString x = "Pineapple";
QString y = x.left(4);      // y == "Pine"

See also right(), mid(), and startsWith().

QString QString::leftJustified(int width, QChar fill = QLatin1Char( ' ' ), bool truncate = false) const

Returns a string of size width that contains this string padded by the fill character.

If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.

QString s = "apple";
QString t = s.leftJustified(8, '.');    // t == "apple..."

If truncate is true and the size() of the string is more than width, then any characters in a copy of the string after position width are removed, and the copy is returned.

QString str = "Pineapple";
str = str.leftJustified(5, '.', true);    // str == "Pinea"

See also rightJustified().

QStringRef QString::leftRef(int n) const

Returns a substring reference to the n leftmost characters of the string.

If n is greater than or equal to size(), or less than zero, a reference to the entire string is returned.

QString x = "Pineapple";
QStringRef y = x.leftRef(4);        // y == "Pine"

This function was introduced in Qt 4.4.

See also left(), rightRef(), midRef(), and startsWith().

int QString::length() const

Returns the number of characters in this string. Equivalent to size().

See also resize().

[static] int QString::localeAwareCompare(const QString &s1, const QString &s2)

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

On macOS and iOS this function compares according the "Order for sorted lists" setting in the International preferences panel.

See also compare() and QLocale.

int QString::localeAwareCompare(const QString &other) const

This function overloads localeAwareCompare().

Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

Same as localeAwareCompare(*this, other).

int QString::localeAwareCompare(const QStringRef &other) const

This function overloads localeAwareCompare().

Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

Same as localeAwareCompare(*this, other).

This function was introduced in Qt 4.5.

[static] int QString::localeAwareCompare(const QString &s1, const QStringRef &s2)

This function overloads localeAwareCompare().

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

This function was introduced in Qt 4.5.

QString QString::mid(int position, int n = -1) const

Returns a string that contains n characters of this string, starting at the specified position index.

Returns a null string if the position index exceeds the length of the string. If there are less than n characters available in the string starting at the given position, or if n is -1 (default), the function returns all characters that are available from the specified position.

Example:

QString x = "Nine pineapples";
QString y = x.mid(5, 4);            // y == "pine"
QString z = x.mid(5);               // z == "pineapples"

See also left() and right().

QStringRef QString::midRef(int position, int n = -1) const

Returns a substring reference to n characters of this string, starting at the specified position.

If the position exceeds the length of the string, a null reference is returned.

If there are less than n characters available in the string, starting at the given position, or if n is -1 (default), the function returns all characters from the specified position onwards.

Example:

QString x = "Nine pineapples";
QStringRef y = x.midRef(5, 4);      // y == "pine"
QStringRef z = x.midRef(5);         // z == "pineapples"

This function was introduced in Qt 4.4.

See also mid(), leftRef(), and rightRef().

QString QString::normalized(NormalizationForm mode, QChar::UnicodeVersion version = QChar::Unicode_Unassigned) const

Returns the string in the given Unicode normalization mode, according to the given version of the Unicode standard.

[static] QString QString::number(long n, int base = 10)

Returns a string equivalent of the number n according to the specified base.

The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.

The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.

long a = 63;
QString s = QString::number(a, 16);             // s == "3f"
QString t = QString::number(a, 16).toUpper();     // t == "3F"

See also setNum().

[static] QString QString::number(uint n, int base = 10)

This is an overloaded function.

[static] QString QString::number(int n, int base = 10)

This is an overloaded function.

[static] QString QString::number(ulong n, int base = 10)

This is an overloaded function.

[static] QString QString::number(qlonglong n, int base = 10)

This is an overloaded function.

[static] QString QString::number(qulonglong n, int base = 10)

This is an overloaded function.

[static] QString QString::number(double n, char format = 'g', int precision = 6)

Returns a string equivalent of the number n, formatted according to the specified format and precision. See Argument Formats for details.

Unlike QLocale::toString(), this function does not honor the user's locale settings.

See also setNum() and QLocale::toString().

QString &QString::prepend(const QString &str)

Prepends the string str to the beginning of this string and returns a reference to this string.

Example:

QString x = "ship";
QString y = "air";
x.prepend(y);
// x == "airship"

See also append() and insert().

QString &QString::prepend(const QChar *str, int len)

This function overloads prepend().

Prepends len characters from the QChar array str to this string and returns a reference to this string.

This function was introduced in Qt 5.5.

QString &QString::prepend(QChar ch)

This function overloads prepend().

Prepends the character ch to this string.

QString &QString::prepend(const QStringRef &str)

This function overloads prepend().

Prepends the string reference str to the beginning of this string and returns a reference to this string.

This function was introduced in Qt 5.5.

QString &QString::prepend(QLatin1String str)

This function overloads prepend().

Prepends the Latin-1 string str to this string.

QString &QString::prepend(const char *str)

This function overloads prepend().

Prepends the string str to this string. The const char pointer is converted to Unicode using the fromUtf8() function.

You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

QString &QString::prepend(const QByteArray &ba)

This function overloads prepend().

Prepends the byte array ba to this string. The byte array is converted to Unicode using the fromUtf8() function.

You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

void QString::push_back(const QString &other)

This function is provided for STL compatibility, appending the given other string onto the end of this string. It is equivalent to append(other).

See also append().

void QString::push_back(QChar ch)

This is an overloaded function.

Appends the given ch character onto the end of this string.

void QString::push_front(const QString &other)

This function is provided for STL compatibility, prepending the given other string to the beginning of this string. It is equivalent to prepend(other).

See also prepend().

void QString::push_front(QChar ch)

This is an overloaded function.

Prepends the given ch character to the beginning of this string.

reverse_iterator QString::rbegin()

Returns a STL-style reverse iterator pointing to the first character in the string, in reverse order.

This function was introduced in Qt 5.6.

See also begin(), crbegin(), and rend().

const_reverse_iterator QString::rbegin() const

This is an overloaded function.

This function was introduced in Qt 5.6.

QString &QString::remove(int position, int n)

Removes n characters from the string, starting at the given position index, and returns a reference to the string.

If the specified position index is within the string, but position + n is beyond the end of the string, the string is truncated at the specified position.

QString s = "Montreal";
s.remove(1, 4);
// s == "Meal"

See also insert() and replace().

QString &QString::remove(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive)

Removes every occurrence of the character ch in this string, and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString t = "Ali Baba";
t.remove(QChar('a'), Qt::CaseInsensitive);
// t == "li Bb"

This is the same as replace(ch, "", cs).

See also replace().

QString &QString::remove(const QString &str, Qt::CaseSensitivity cs = Qt::CaseSensitive)

Removes every occurrence of the given str string in this string, and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This is the same as replace(str, "", cs).

See also replace().

QString &QString::remove(const QRegExp &rx)

Removes every occurrence of the regular expression rx in the string, and returns a reference to the string. For example:

QString r = "Telephone";
r.remove(QRegExp("[aeiou]."));
// r == "The"

See also indexOf(), lastIndexOf(), and replace().

QString &QString::remove(const QRegularExpression &re)

Removes every occurrence of the regular expression re in the string, and returns a reference to the string. For example:

QString r = "Telephone";
r.remove(QRegularExpression("[aeiou]."));
// r == "The"

This function was introduced in Qt 5.0.

See also indexOf(), lastIndexOf(), and replace().

reverse_iterator QString::rend()

Returns a STL-style reverse iterator pointing to one past the last character in the string, in reverse order.

This function was introduced in Qt 5.6.

See also end(), crend(), and rbegin().

const_reverse_iterator QString::rend() const

This is an overloaded function.

This function was introduced in Qt 5.6.

QString QString::repeated(int times) const

Returns a copy of this string repeated the specified number of times.

If times is less than 1, an empty string is returned.

Example:

QString str("ab");
str.repeated(4);            // returns "abababab"

This function was introduced in Qt 4.5.

QString &QString::replace(int position, int n, const QString &after)

Replaces n characters beginning at index position with the string after and returns a reference to this string.

Note: If the specified position index is within the string, but position + n goes outside the strings range, then n will be adjusted to stop at the end of the string.

Example:

QString x = "Say yes!";
QString y = "no";
x.replace(4, 3, y);
// x == "Say no!"

See also insert() and remove().

QString &QString::replace(int position, int n, const QChar *unicode, int size)

This function overloads replace().

Replaces n characters beginning at index position with the first size characters of the QChar array unicode and returns a reference to this string.

QString &QString::replace(int position, int n, QChar after)

This function overloads replace().

Replaces n characters beginning at index position with the character after and returns a reference to this string.

QString &QString::replace(QChar before, QChar after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the character before with the character after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

QString &QString::replace(const QChar *before, int blen, const QChar *after, int alen, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces each occurrence in this string of the first blen characters of before with the first alen characters of after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.5.

QString &QString::replace(QLatin1String before, QLatin1String after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the string before with the string after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Note: The text is not rescanned after a replacement.

This function was introduced in Qt 4.5.

QString &QString::replace(QLatin1String before, const QString &after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the string before with the string after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Note: The text is not rescanned after a replacement.

This function was introduced in Qt 4.5.

QString &QString::replace(const QString &before, QLatin1String after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the string before with the string after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Note: The text is not rescanned after a replacement.

This function was introduced in Qt 4.5.

QString &QString::replace(const QString &before, const QString &after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the string before with the string after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

QString str = "colour behaviour flavour neighbour";
str.replace(QString("ou"), QString("o"));
// str == "color behavior flavor neighbor"

Note: The replacement text is not rescanned after it is inserted.

Example:

QString equis = "xxxxxx";
equis.replace("xx", "x");
// equis == "xxx"

QString &QString::replace(QChar ch, const QString &after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the character ch in the string with after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

QString &QString::replace(QChar c, QLatin1String after, Qt::CaseSensitivity cs = Qt::CaseSensitive)

This function overloads replace().

Replaces every occurrence of the character c with the string after and returns a reference to this string.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Note: The text is not rescanned after a replacement.

This function was introduced in Qt 4.5.

QString &QString::replace(const QRegExp &rx, const QString &after)

This function overloads replace().

Replaces every occurrence of the regular expression rx in the string with after. Returns a reference to the string. For example:

QString s = "Banana";
s.replace(QRegExp("a[mn]"), "ox");
// s == "Boxoxa"

For regular expressions containing capturing parentheses, occurrences of \1, \2, ..., in after are replaced with rx.cap(1), cap(2), ...

QString t = "A <i>bon mot</i>.";
t.replace(QRegExp("<i>([^<]*)</i>"), "\\emph{\\1}");
// t == "A \\emph{bon mot}."

See also indexOf(), lastIndexOf(), remove(), and QRegExp::cap().

QString &QString::replace(const QRegularExpression &re, const QString &after)

This function overloads replace().

Replaces every occurrence of the regular expression re in the string with after. Returns a reference to the string. For example:

QString s = "Banana";
s.replace(QRegularExpression("a[mn]"), "ox");
// s == "Boxoxa"

For regular expressions containing capturing groups, occurrences of \1, \2, ..., in after are replaced with the string captured by the corresponding capturing group.

QString t = "A <i>bon mot</i>.";
t.replace(QRegularExpression("<i>([^<]*)</i>"), "\\emph{\\1}");
// t == "A \\emph{bon mot}."

This function was introduced in Qt 5.0.

See also indexOf(), lastIndexOf(), remove(), QRegularExpression, and QRegularExpressionMatch.

void QString::reserve(int size)

Attempts to allocate memory for at least size characters. If you know in advance how large the string will be, you can call this function, and if you resize the string often you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QString will be a bit slower.

The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the string, call resize().

This function is useful for code that needs to build up a long string and wants to avoid repeated reallocation. In this example, we want to add to the string until some condition is true, and we're fairly sure that size is large enough to make a call to reserve() worthwhile:

QString result;
int maxSize;
bool condition;
QChar nextChar;

result.reserve(maxSize);

while (condition)
    result.append(nextChar);

result.squeeze();

See also squeeze() and capacity().

void QString::resize(int size)

Sets the size of the string to size characters.

If size is greater than the current size, the string is extended to make it size characters long with the extra characters added to the end. The new characters are uninitialized.

If size is less than the current size, characters are removed from the end.

Example:

QString s = "Hello world";
s.resize(5);
// s == "Hello"

s.resize(8);
// s == "Hello???" (where ? stands for any character)

If you want to append a certain number of identical characters to the string, use the resize(int, QChar) overload.

If you want to expand the string so that it reaches a certain width and fill the new positions with a particular character, use the leftJustified() function:

If size is negative, it is equivalent to passing zero.

QString r = "Hello";
r = r.leftJustified(10, ' ');
// r == "Hello     "

See also truncate() and reserve().

void QString::resize(int size, QChar fillChar)

This is an overloaded function.

Unlike resize(int), this overload initializes the new characters to fillChar:

QString t = "Hello";
r.resize(t.size() + 10, 'X');
// t == "HelloXXXXXXXXXX"

This function was introduced in Qt 5.7.

QString QString::right(int n) const

Returns a substring that contains the n rightmost characters of the string.

The entire string is returned if n is greater than or equal to size(), or less than zero.

QString x = "Pineapple";
QString y = x.right(5);      // y == "apple"

See also left(), mid(), and endsWith().

QString QString::rightJustified(int width, QChar fill = QLatin1Char( ' ' ), bool truncate = false) const

Returns a string of size() width that contains the fill character followed by the string. For example:

QString s = "apple";
QString t = s.rightJustified(8, '.');    // t == "...apple"

If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.

If truncate is true and the size() of the string is more than width, then the resulting string is truncated at position width.

QString str = "Pineapple";
str = str.rightJustified(5, '.', true);    // str == "Pinea"

See also leftJustified().

QStringRef QString::rightRef(int n) const

Returns a substring reference to the n rightmost characters of the string.

If n is greater than or equal to size(), or less than zero, a reference to the entire string is returned.

QString x = "Pineapple";
QStringRef y = x.rightRef(5);       // y == "apple"

This function was introduced in Qt 4.4.

See also right(), leftRef(), midRef(), and endsWith().

QString QString::section(QChar sep, int start, int end = -1, SectionFlags flags = SectionDefault) const

This function returns a section of the string.

This string is treated as a sequence of fields separated by the character, sep. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included. Fields are numbered 0, 1, 2, etc., counting from the left, and -1, -2, etc., counting from right to left.

The flags argument can be used to affect some aspects of the function's behavior, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.

QString str;
QString csv = "forename,middlename,surname,phone";
QString path = "/usr/local/bin/myapp"; // First field is empty
QString::SectionFlag flag = QString::SectionSkipEmpty;

str = csv.section(',', 2, 2);   // str == "surname"
str = path.section('/', 3, 4);  // str == "bin/myapp"
str = path.section('/', 3, 3, flag); // str == "myapp"

If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.

str = csv.section(',', -3, -2);  // str == "middlename,surname"
str = path.section('/', -1); // str == "myapp"

See also split().

QString QString::section(const QString &sep, int start, int end = -1, SectionFlags flags = SectionDefault) const

This function overloads section().

QString str;
QString data = "forename**middlename**surname**phone";

str = data.section("**", 2, 2); // str == "surname"
str = data.section("**", -3, -2); // str == "middlename**surname"

See also split().

QString QString::section(const QRegExp &reg, int start, int end = -1, SectionFlags flags = SectionDefault) const

This function overloads section().

This string is treated as a sequence of fields separated by the regular expression, reg.

QString line = "forename\tmiddlename  surname \t \t phone";
QRegExp sep("\\s+");
str = line.section(sep, 2, 2); // str == "surname"
str = line.section(sep, -3, -2); // str == "middlename  surname"

Warning: Using this QRegExp version is much more expensive than the overloaded string and character versions.

See also split() and simplified().

QString QString::section(const QRegularExpression &re, int start, int end = -1, SectionFlags flags = SectionDefault) const

This function overloads section().

This string is treated as a sequence of fields separated by the regular expression, re.

QString line = "forename\tmiddlename  surname \t \t phone";
QRegularExpression sep("\\s+");
str = line.section(sep, 2, 2); // str == "surname"
str = line.section(sep, -3, -2); // str == "middlename  surname"

Warning: Using this QRegularExpression version is much more expensive than the overloaded string and character versions.

This function was introduced in Qt 5.0.

See also split() and simplified().

QString &QString::setNum(int n, int base = 10)

Sets the string to the printed value of n in the specified base, and returns a reference to the string.

The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.

QString str;
str.setNum(1234);       // str == "1234"

The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.

QString &QString::setNum(ushort n, int base = 10)

This is an overloaded function.

QString &QString::setNum(short n, int base = 10)

This is an overloaded function.

QString &QString::setNum(uint n, int base = 10)

This is an overloaded function.

QString &QString::setNum(long n, int base = 10)

This is an overloaded function.

QString &QString::setNum(ulong n, int base = 10)

This is an overloaded function.

QString &QString::setNum(qlonglong n, int base = 10)

This is an overloaded function.

QString &QString::setNum(qulonglong n, int base = 10)

This is an overloaded function.

QString &QString::setNum(float n, char format = 'g', int precision = 6)

This is an overloaded function.

Sets the string to the printed value of n, formatted according to the given format and precision, and returns a reference to the string.

The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.

QString &QString::setNum(double n, char format = 'g', int precision = 6)

This is an overloaded function.

Sets the string to the printed value of n, formatted according to the given format and precision, and returns a reference to the string.

The format can be 'e', 'E', 'f', 'g' or 'G' (see Argument Formats for an explanation of the formats).

The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.

QString &QString::setRawData(const QChar *unicode, int size)