Class Object < BasicObject

A duck-type assistant method. For example, Active Support extends Date to define an acts_like_date? method, and extends Time to define acts_like_time?. As a result, we can do “x.acts_like?(:time)” and “x.acts_like?(:date)” to do duck-type-safe comparisons, since classes that we want to act like Time simply need to define an acts_like_time? method.

An object is blank if it’s false, empty, or a whitespace string. For example, “”, “ ”, nil, [], and {} are all blank.

This simplifies:

if address.nil? || address.empty?

…to:

if address.blank?

Can you safely dup this object?

False for nil, false, true, symbols, numbers, class and module objects; true otherwise.

Returns true if this object is included in the argument(s). Argument must be any object which responds to #include? or optionally, multiple arguments can be passed in. Usage:

characters = ["Konata", "Kagami", "Tsukasa"]
"Konata".in?(characters) # => true

character = "Konata"
character.in?("Konata", "Kagami", "Tsukasa") # => true

This will throw an ArgumentError if a single argument is passed in and it doesn’t respond to #include?.

Returns object if it’s present? otherwise returns nil. object.presence is equivalent to object.present? ? object : nil.

This is handy for any representation of objects where blank is the same as not present at all. For example, this simplifies a common check for HTTP POST/query parameters:

state   = params[:state]   if params[:state].present?
country = params[:country] if params[:country].present?
region  = state || country || 'US'

…becomes:

region = params[:state].presence || params[:country].presence || 'US'

An object is present if it’s not blank?.

Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.

Alias of to_s.

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

Note: This method is defined as a default implementation for all Objects for Hash#to_query to work.

Invokes the method identified by the symbol method, passing it any arguments and/or the block specified, just like the regular Ruby Object#send does.

Unlike that method however, a NoMethodError exception will not be raised and nil will be returned instead, if the receiving object is a nil object or NilClass.

If try is called without a method to call, it will yield any given block with the object.

Please also note that try is defined on Object, therefore it won’t work with subclasses of BasicObject. For example, using try with SimpleDelegator will delegate try to target instead of calling it on delegator itself.

Examples

Without try

@person && @person.name

or

@person ? @person.name : nil

With try

@person.try(:name)

try also accepts arguments and/or a block, for the method it is trying

Person.try(:find, 1)
@people.try(:collect) {|p| p.name}

Without a method argument try will yield to the block unless the receiver is nil.

@person.try { |p| "#{p.first_name} #{p.last_name}" }

An elegant way to factor duplication out of options passed to a series of method calls. Each method called in the block, with the block variable as the receiver, will have its options merged with the default options hash provided. Each method called on the block variable must take an options hash as its final argument.

Without with_options>, this code contains duplication:

class Account < ActiveRecord::Base
  has_many :customers, :dependent => :destroy
  has_many :products,  :dependent => :destroy
  has_many :invoices,  :dependent => :destroy
  has_many :expenses,  :dependent => :destroy
end

Using with_options, we can remove the duplication:

class Account < ActiveRecord::Base
  with_options :dependent => :destroy do |assoc|
    assoc.has_many :customers
    assoc.has_many :products
    assoc.has_many :invoices
    assoc.has_many :expenses
  end
end

It can also be used with an explicit receiver:

I18n.with_options :locale => user.locale, :scope => "newsletter" do |i18n|
  subject i18n.t :subject
  body    i18n.t :body, :user_name => user.name
end

with_options can also be nested since the call is forwarded to its receiver. Each nesting level will merge inherited defaults in addition to their own.