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Document Active Support's Module::delegate. Closes #5002.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4329 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
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commit befd62c2fc04356980c4de493ffdee40e7a36c87 1 parent 0adcd81
@jeremy jeremy authored
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2  activesupport/CHANGELOG
@@ -1,5 +1,7 @@
*SVN*
+* Document Module::delegate. #5002 [pergesu@gmail.com]
+
* Replace alias method chaining with Module#alias_method_chain. [Marcel Molina Jr.]
* Strip out punctuation on predicates or bang methods being aliased with alias_method_chain since target?_without_feature is not a valid method name. Add tests for Module#alias_method_chain. [Marcel Molina Jr.]
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29 activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -1,8 +1,33 @@
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>
+ #
+ # With multiple delegates to the same target are allowed:
+ # class Foo < ActiveRecord::Base
+ # 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"
+ 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|
@@ -13,4 +38,4 @@ def #{method}(*args, &block)
EOS
end
end
-end
+end
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