Class Array < Object

Wraps its argument in an array unless it is already an array (or array-like).

Specifically:

• If the argument is nil an empty list is returned.

• Otherwise, if the argument responds to to_ary it is invoked, and its result returned.

• Otherwise, returns an array with the argument as its single element.

  ::wrap # => [] ::wrap([1, 2, 3]) # => [1, 2, 3] ::wrap # => [0]

This method is similar in purpose to Kernel#Array, but there are some differences:

• If the argument responds to to_ary the method is invoked. Kernel#Array

moves on to try to_a if the returned value is nil, but Array.wrap returns such a nil right away.

• If the returned value from to_ary is neither nil nor an Array object, Kernel#Array

raises an exception, while Array.wrap does not, it just returns the value.

• It does not call to_a on the argument, though special-cases nil to return an empty array.

The last point is particularly worth comparing for some enumerables:

Array(:foo => :bar)      # => [[:foo, :bar]]
Array.wrap(:foo => :bar) # => [{:foo => :bar}]

Array("foo\nbar")        # => ["foo\n", "bar"], in Ruby 1.8
Array.wrap("foo\nbar")   # => ["foo\nbar"]

There’s also a related idiom that uses the splat operator:

[*object]

which returns [nil] for nil, and calls to Array(object) otherwise.

Thus, in this case the behavior is different for nil, and the differences with Kernel#Array explained above apply to the rest of +object+s.

Extracts options from a set of arguments. Removes and returns the last element in the array if it’s a hash, otherwise returns a blank hash.

def options(*args)
  args.extract_options!
end

options(1, 2)           # => {}
options(1, 2, :a => :b) # => {:a=>:b}

Equal to self[4].

Equal to self[41]. Also known as accessing “the reddit”.

Equal to self[3].

Returns the tail of the array from position.

%w( a b c d ).from(0)  # => %w( a b c d )
%w( a b c d ).from(2)  # => %w( c d )
%w( a b c d ).from(10) # => %w()
%w().from(0)           # => %w()

Splits or iterates over the array in number of groups, padding any remaining slots with fill_with unless it is false.

%w(1 2 3 4 5 6 7 8 9 10).in_groups(3) {|group| p group}
["1", "2", "3", "4"]
["5", "6", "7", nil]
["8", "9", "10", nil]

%w(1 2 3 4 5 6 7).in_groups(3, ' ') {|group| p group}
["1", "2", "3"]
["4", "5", " "]
["6", "7", " "]

%w(1 2 3 4 5 6 7).in_groups(3, false) {|group| p group}
["1", "2", "3"]
["4", "5"]
["6", "7"]

Splits or iterates over the array in groups of size number, padding any remaining slots with fill_with unless it is false.

%w(1 2 3 4 5 6 7).in_groups_of(3) {|group| p group}
["1", "2", "3"]
["4", "5", "6"]
["7", nil, nil]

%w(1 2 3).in_groups_of(2, ' ') {|group| p group}
["1", "2"]
["3", " "]

%w(1 2 3).in_groups_of(2, false) {|group| p group}
["1", "2"]
["3"]

Backport of #sample based on Marc-Andre Lafortune’s github.com/marcandre/backports/ Returns a random element or n random elements from the array. If the array is empty and n is nil, returns nil. If n is passed and its value is less than 0, it raises an ArgumentError exception. If the value of n is equal or greater than 0 it returns [].

[1,2,3,4,5,6].sample     # => 4
[1,2,3,4,5,6].sample(3)  # => [2, 4, 5]
[1,2,3,4,5,6].sample(-3) # => ArgumentError: negative array size
           [].sample     # => nil
           [].sample(3)  # => []

Equal to self[1].

Divides the array into one or more subarrays based on a delimiting value or the result of an optional block.

[1, 2, 3, 4, 5].split(3)                # => [[1, 2], [4, 5]]
(1..10).to_a.split { |i| i % 3 == 0 }   # => [[1, 2], [4, 5], [7, 8], [10]]

Equal to self[2].

Returns the beginning of the array up to position.

%w( a b c d ).to(0)  # => %w( a )
%w( a b c d ).to(2)  # => %w( a b c )
%w( a b c d ).to(10) # => %w( a b c d )
%w().to(0)           # => %w()

Converts a collection of elements into a formatted string by calling to_s on all elements and joining them:

Blog.all.to_formatted_s # => "First PostSecond PostThird Post"

Adding in the :db argument as the format yields a comma separated id list:

Blog.all.to_formatted_s(:db) # => "1,2,3"

Calls to_param on all its elements and joins the result with slashes. This is used by url_for in Action Pack.

Converts an array into a string suitable for use as a URL query string, using the given key as the param name.

['Rails', 'coding'].to_query('hobbies') # => "hobbies%5B%5D=Rails&hobbies%5B%5D=coding"

Converts the array to a comma-separated sentence where the last element is joined by the connector word. Options:

• :words_connector - The sign or word used to join the elements in arrays with two or more elements (default: ", ")

• :two_words_connector - The sign or word used to join the elements in arrays with two elements (default: " and ")

• :last_word_connector - The sign or word used to join the last element in arrays with three or more elements (default: ", and ")

Returns a string that represents the array in XML by invoking to_xml on each element. Active Record collections delegate their representation in XML to this method.

All elements are expected to respond to to_xml, if any of them does not then an exception is raised.

The root node reflects the class name of the first element in plural if all elements belong to the same type and that’s not Hash:

customer.projects.to_xml

<?xml version="1.0" encoding="UTF-8"?>
<projects type="array">
  <project>
    <amount type="decimal">20000.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-09</deal-date>
    ...
  </project>
  <project>
    <amount type="decimal">57230.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-15</deal-date>
    ...
  </project>
</projects>

Otherwise the root element is “records”:

[{:foo => 1, :bar => 2}, {:baz => 3}].to_xml

<xxml version="1.0" encoding="UTF-8"?>
<records type="array">
  <record>
    <bar type="integer">2<%rbar>
    <foo type="integer">1</foo>
  <%rrecord>
  <record>
    <baz type="integer">3</baz>
  <%rrecord>
</records>

If the collection is empty the root element is “nil-classes” by default:

[].to_xml

<?xml version="1.0" encoding="UTF-8"?>
<nil-classes type="array"/>

To ensure a meaningful root element use the :root option:

customer_with_no_projects.projects.to_xml(:root => "projects")

<xxml version="1.0" encoding="UTF-8"?>
<projects type="array"/>

By default name of the node for the children of root is root.singularize. You can change it with the :children option.

The options hash is passed downwards:

Message.all.to_xml(:skip_types => true)

<xxml version="1.0" encoding="UTF-8"?>
<messages>
  <message>
    <created-at>2008-03-07T09:58:18+01:00<%rcreated-at>
    <id>1</d>
    <name>1<%rname>
    <updated-at>2008-03-07T09:58:18+01:00</pdated-at>
    <user-id>1<%ruser-id>
  </essage>
<%rmessages>

Returns an unique array based on the criteria given as a Proc.

[1, 2, 3, 4].uniq_by { |i| i.odd? } # => [1, 2]

Same as #uniq_by, but modifies self.