Object

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.

   # File lib/active_support/core_ext/object/acts_like.rb, line 7
7:   def acts_like?(duck)
8:     respond_to? :"acts_like_#{duck}?"
9:   end

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

This simplifies:

  if !address.nil? && !address.empty?

…to:

  if !address.blank?

    # File lib/active_support/core_ext/object/blank.rb, line 12
12:   def blank?
13:     respond_to?(:empty?) ? empty? : !self
14:   end

Can you safely .dup this object? False for nil, false, true, symbols, numbers, class and module objects; true otherwise.

    # File lib/active_support/core_ext/object/duplicable.rb, line 20
20:   def duplicable?
21:     true
22:   end

Returns object if it’s # 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'

    # File lib/active_support/core_ext/object/blank.rb, line 35
35:   def presence
36:     self if present?
37:   end

An object is present if it’s not blank.

    # File lib/active_support/core_ext/object/blank.rb, line 17
17:   def present?
18:     !blank?
19:   end

Returns value after yielding value to the block. This simplifies the process of constructing an object, performing work on the object, and then returning the object from a method. It is a Ruby-ized realization of the K combinator, courtesy of Mikael Brockman.

Examples

 # Without returning
 def foo
   values = []
   values << "bar"
   values << "baz"
   return values
 end

 foo # => ['bar', 'baz']

 # returning with a local variable
 def foo
   returning values = [] do
     values << 'bar'
     values << 'baz'
   end
 end

 foo # => ['bar', 'baz']

 # returning with a block argument
 def foo
   returning [] do |values|
     values << 'bar'
     values << 'baz'
   end
 end

 foo # => ['bar', 'baz']

    # File lib/active_support/core_ext/object/returning.rb, line 38
38:   def returning(value)
39:     ActiveSupport::Deprecation.warn('Object#returning has been deprecated in favor of Object#tap.', caller)
40:     yield(value)
41:     value
42:   end

Alias of to_s.

   # File lib/active_support/core_ext/object/to_param.rb, line 5
5:   def to_param
6:     to_s
7:   end

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.

    # File lib/active_support/core_ext/object/to_query.rb, line 8
 8:   def to_query(key)
 9:     require 'cgi' unless defined?(CGI) && defined?(CGI::escape)
10:     "#{CGI.escape(key.to_s).gsub(/%(5B|5D)/n) { [$1].pack('H*') }}=#{CGI.escape(to_param.to_s)}"
11:   end

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.

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}

    # File lib/active_support/core_ext/object/try.rb, line 25
25:   def try(method, *args, &block)
26:     send(method, *args, &block)
27:   end

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.

  with_options :order => 'created_at', :class_name => 'Comment' do |post|
    post.has_many :comments, :conditions => ['approved = ?', true], :dependent => :delete_all
    post.has_many :unapproved_comments, :conditions => ['approved = ?', false]
    post.has_many :all_comments
  end

Can also be used with an explicit receiver:

  map.with_options :controller => "people" do |people|
    people.connect "/people",     :action => "index"
    people.connect "/people/:id", :action => "show"
  end

    # File lib/active_support/core_ext/object/with_options.rb, line 23
23:   def with_options(options)
24:     yield ActiveSupport::OptionMerger.new(self, options)
25:   end