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tag: v2.0.0_RC2
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class Module
# Provides a delegate class method to easily expose contained objects' methods
# as your own. Pass one or more methods (specified as symbols or strings)
# and the name of the target object as the final :to option (also a symbol
# or string). At least one method and the :to option are required.
#
# Delegation is particularly useful with Active Record associations:
# class Greeter < ActiveRecord::Base
# def hello() "hello" end
# def goodbye() "goodbye" end
# end
#
# class Foo < ActiveRecord::Base
# belongs_to :greeter
# delegate :hello, :to => :greeter
# end
#
# Foo.new.hello # => "hello"
# Foo.new.goodbye # => NoMethodError: undefined method `goodbye' for #<Foo:0x1af30c>
#
# Multiple delegates to the same target are allowed:
# class Foo < ActiveRecord::Base
# belongs_to :greeter
# delegate :hello, :goodbye, :to => :greeter
# end
#
# Foo.new.goodbye # => "goodbye"
def delegate(*methods)
options = methods.pop
unless options.is_a?(Hash) && to = options[:to]
raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
end
methods.each do |method|
module_eval(<<-EOS, "(__DELEGATION__)", 1)
def #{method}(*args, &block)
#{to}.__send__(#{method.inspect}, *args, &block)
end
EOS
end
end
end
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