From: "Jørgen P. Tjernø" <jorgen@...>
Date: 2006-07-19T01:54:05+09:00
Subject: Re: Difference between include and require for modules?

Jatinder Singh wrote:
> What I understand from require statement is that the argument to it is a
> file, where as include requires module/class name.
> 
> But once I do a require for a specific ruby file which has various modules
> and classes, doesn't these classes/modules get included automatically?
> infact they do get automatically as I have tried doing so.
> 
> But in various files of ruby library I found that people use include
> "modulename" after a require statement for the file which contains that
> module.
> 
> Any reasons?
> 
> Thanks,
> Jatinder
> 

Require is purely used to 'embed' files in other files.

Include is used on modules, and adds so-called "MixIn"-functionality.
It means you "import" the methods of the given Module into the current 
class (or Module?).

So, basically, you have a Module that provides some semi-generic 
functionality, then you have a class that wants to take advantage of 
this functionality.

Example:

module A
   def b
     "bar"
   end
end

class B
   include A
end

foo = B.new
foo.b
=> "bar"


I hope this helps!

Ps. this explanation might be horrible, and it might be wrong; I'm not a 
"professional" rubyist. ;-)

-- 
Kindest regards / Med vennlig hilsen,
  J�rgen P. Tjern�
  <jorgen@devsoft.no>