From: Brian Candler <b.candler@...>
Date: 2009-06-04T23:06:11+09:00
Subject: Re: Ruby Execution

Mike Stephens wrote:
> Brian Candler wrote:
>> P.S. If you want to defer loading of classes until when they are used, 
>> have a look at Kernel#autoload
> 
> Is this the norm? I would have thought it would be a real problem 
> parsing big frameworks with myriads of classes everytime you want to 
> make a simple call.

Once a library has been require'd once, then the fact that this has been 
done is recorded (in variable $LOADED_FEATURES), and so it won't be 
loaded again. If you want to check this out: require returns 'true' if 
it had to load something, and 'false' if it didn't.

Autoload goes one stage further: it won't load the file unless the 
constant doesn't exist.

-------------------------------------------------------- Kernel#autoload
     autoload(module, filename)   => nil
------------------------------------------------------------------------
     Registers _filename_ to be loaded (using +Kernel::require+) the
     first time that _module_ (which may be a +String+ or a symbol) is
     accessed.

        autoload(:MyModule, "/usr/local/lib/modules/my_module.rb")

That is: the first time you try to do MyModule.foo, the file is 
required, which (presumably) defines MyModule. Since it now exists, the 
next call to MyModule.bar won't touch any source files.

> Is there a way of keeping a parsed script cached eg 
> for a web site that is handling hundreds of users doing the same sorts 
> of things eg browsing product lists?

As I say, once the file has been loaded, it's loaded.

The only problem comes if you quit the process and restart it, as then 
it obviously has to load everything again from scratch. I wrote 
something which can help with that:
http://github.com/candlerb/snailgun
-- 
Posted via http://www.ruby-forum.com/.