From: Pat Maddox <pergesu@...>
Date: 2006-12-18T02:41:03+09:00
Subject: Re: require, load and include --- what's the difference?

On 12/17/06, matt <matt@kettlewell.net> wrote:
> Hello,
>
> I'm browsing through some code, trying to familiarize myself with the
> language (I have a C++ background, with only a #include), and I realize
> that there are 3 calls that I'm trying to wrap my head around.
>
> Here's my stab:
>
> Require -- seems to include another file to gain access to other
> classes, modules, and global data. This seems to be equivalent to a C++
> include, with inclusion guards

Right

> Load -- seems to be the same as require, but will actually reload the
> data every time it is called, where require will load once and cache the
> file. This seems to be equivalent to C++ include, with out inclusion
> guards.

Right

> Include -- seems to include a module name from a pre-determined path,
> but not classes (unless encapsulated within a module).  Would this be
> similar to a C++ namespace being given the include directory at compile
> time?

include mixes in a module, so the methods defined on the module become
instance methods on the class.

module Foo
  def foo; "foo"; end
end

class Boring
  include Foo
end

Boring.new.foo   => "foo"

> So a couple of things here, are my understandings of the 3 methods
> close, if not, could someone please expand on them.  The other is what's
> the advantage of include vs require?  I mean, why would I include a
> module, rather than require it's filename?

load and require are for loading a file into your code.  include is
used to actually enhance an individual object (because a class itself
is an object).

Pat