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Document the changes to delegate in the guides

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1 parent 2310db3 commit 3b1537a7d1c19d7f4ab6ae1a405ec4c2c186a55c @dasch dasch committed with dasch Sep 1, 2011
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  1. +20 −0 guides/source/active_support_core_extensions.textile
@@ -883,6 +883,26 @@ delegate :size, :to => :attachment, :prefix => :avatar
In the previous example the macro generates +avatar_size+ rather than +size+.
+WARNING: You can only delegate to public methods on the target object. Trying to delegate to a private or protected method will raise a +NoMethodError+ when the delegate is called.
+If you need to delegate to a private or protected method, you will need to implement the delegation method yourself. It's usually rather simple to do using +__send__+:
+class Wrapper
+ def initialize
+ # Target#zizzle is a private method.
+ @target =
+ end
+ def zizzle(*args, &block)
+ # __send__ circumvents the private/protected mechanism.
+ @target.__send__(:zizzle, *args, &block)
+ end
+Since +__send__+ can be used to call private and protected methods, this will not raise a +NoMethodError+.
NOTE: Defined in +active_support/core_ext/module/delegation.rb+
h4. Redefining Methods

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