From: John Wilger <johnwilger@...>
Date: 2006-12-18T02:52:01+09:00
Subject: Re: require, load and include --- what's the difference?

On Dec 17, 9:19 am, matt <m...@kettlewell.net> wrote:
> 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
>
> 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.

Basically correct on these two.

> 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?

<snip>

> what's
> the advantage of include vs require?  I mean, why would I include a
> module, rather than require it's filename?

Include doesn't really have anything to do with files or paths. For
instance, the following code could all be in the same file:

## BEGIN ##
Woden:~ jwilger$ irb
>> module Foo
>>   def hello
>>     "defined in module Foo"
>>   end
>> end
=> nil
>>
?> class Bar
>>   include Foo
>> end
=> Bar
>>
?> x = Bar.new
=> #<Bar:0x12a1838>
>> x.hello
=> "defined in module Foo"
## END ##

When used this way, modules and include are Ruby's preferred way to
implement that which would be achieved via multiple inheritance in some
other languages.