From: Frederick Cheung <frederick.cheung@...>
Date: 2008-08-20T00:12:21+09:00
Subject: Re: Array API


On 19 Aug 2008, at 15:09, Robert Klemme wrote:
>>>
>>> How it is possible that we are able to use enumerable sort_by  
>>> method for
>>> an array of object?
>>>
>> Because that's what including a module does: it adds the methods  
>> defined in
>> the module to the class.
>
> This is only true in a very general sense, i.e. if you want to express
> with this that you can invoke methods defined in a module on an
> instance of a class that directly or indirectly (!) inherits the
> module.
>
> irb(main):002:0> Array.instance_method :sort_by
> => #<UnboundMethod: Array(Enumerable)#sort_by>
> irb(main):003:0> Array.instance_method :size
> => #<UnboundMethod: Array#size>
>
> Note the difference between #sort_by (defined in Enumerable) and #size
> (defined in Array).
>
> Rather the module is inserted into the lookup path (see output of
> #ancestors above).  Otherwise methods from different modules could not
> invoke each other via super but instead one would overwrite the other:
>

Of course. it would also mean that adding methods to a module after it  
had been included wouldn't work.

Fred