vendor/rails/activesupport/lib/active_support/core_ext/object/misc.rb

   1 class Object
   2   # Returns +value+ after yielding +value+ to the block. This simplifies the
   3   # process of constructing an object, performing work on the object, and then
   4   # returning the object from a method. It is a Ruby-ized realization of the K
   5   # combinator, courtesy of Mikael Brockman.
   6   #
   7   # ==== Examples
   8   #
   9   #  # Without returning
  10   #  def foo
  11   #    values = []
  12   #    values << "bar"
  13   #    values << "baz"
  14   #    return values
  15   #  end
  16   #
  17   #  foo # => ['bar', 'baz']
  18   #
  19   #  # returning with a local variable
  20   #  def foo
  21   #    returning values = [] do
  22   #      values << 'bar'
  23   #      values << 'baz'
  24   #    end
  25   #  end
  26   #
  27   #  foo # => ['bar', 'baz']
  28   #
  29   #  # returning with a block argument
  30   #  def foo
  31   #    returning [] do |values|
  32   #      values << 'bar'
  33   #      values << 'baz'
  34   #    end
  35   #  end
  36   #
  37   #  foo # => ['bar', 'baz']
  38   def returning(value)
  39     yield(value)
  40     value
  41   end
  42
  43   # An elegant way to factor duplication out of options passed to a series of
  44   # method calls. Each method called in the block, with the block variable as
  45   # the receiver, will have its options merged with the default +options+ hash
  46   # provided. Each method called on the block variable must take an options
  47   # hash as its final argument.
  48   #
  49   #   with_options :order => 'created_at', :class_name => 'Comment' do |post|
  50   #     post.has_many :comments, :conditions => ['approved = ?', true], :dependent => :delete_all
  51   #     post.has_many :unapproved_comments, :conditions => ['approved = ?', false]
  52   #     post.has_many :all_comments
  53   #   end
  54   #
  55   # Can also be used with an explicit receiver:
  56   #
  57   #   map.with_options :controller => "people" do |people|
  58   #     people.connect "/people",     :action => "index"
  59   #     people.connect "/people/:id", :action => "show"
  60   #   end
  61   #
  62   def with_options(options)
  63     yield ActiveSupport::OptionMerger.new(self, options)
  64   end
  65
  66   # A duck-type assistant method. For example, Active Support extends Date
  67   # to define an acts_like_date? method, and extends Time to define
  68   # acts_like_time?. As a result, we can do "x.acts_like?(:time)" and
  69   # "x.acts_like?(:date)" to do duck-type-safe comparisons, since classes that
  70   # we want to act like Time simply need to define an acts_like_time? method.
  71   def acts_like?(duck)
  72     respond_to? "acts_like_#{duck}?"
  73   end
  74 end