From: Florian Gilcher <flo@...>
Date: 2009-02-19T00:42:09+09:00
Subject: Re: Dummy question about method in class


On Feb 18, 2009, at 4:36 PM, Valentino Lun wrote:
>
> [1,2,3,4,5].inject { |sum,n| sum+n }
> The inject method in this case is to calculate the sum of array.
>
> I searched the RDoc. Why the inject method is belongs to Enumerable
> Class, but not Array Class?

Enumerable is a Module, not a Class. It can be mixed into other  
classes, so the Class gains the Methods of the module. Arrays uses  
Enumerable instead of implementing #inject on its own, so they respond  
to Enumerables #inject.

As a short presentation, i redefine Enumerable#inspect to do something  
different (never try this at home!):

===
module Enumerable
   def inject
     puts "hey"
   end
end

[].inject #=> puts "hey" now
===

Regards,
Florian Gilcher

--
Florian Gilcher

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