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In Ruby, you can do ... 

Object.send(:public, *Object.private_instance_methods)

... as seen in this answer to another question. This redefines each of the private instance methods of Object, making them public. My question is: how does this work? send is supposed to work with the name of a method, but there do not seem to be methods named public, private, or protected defined on Object (or at least my search-fu has not found them). 

> Object.respond_to?(:public)
=> false
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Pathogen
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1 Answers1

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There is indeed a method called public, but it is defined on Module. This is ok because Object is an instance of Class and the superclass of Class is Module: apart from the slight circularity in the ruby class hierarchy bootstrapping this is just normal ruby inheritance.

Your respond_to? check returns false because by default respond_to? does not check protected or private methods (prior to ruby 2.0 it checked protected methods). You can request that all methods be searched by doing

Object.respond_to?(:public, true)

which does return true.

Frederick Cheung
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  • Interesting! Also, after tinkering around further, I see that making the private methods of Object public does not make the mixed in methods from Module public. – Pathogen Oct 27 '15 at 20:29