From: Robert Dober <robert.dober@...>
Date: 2007-07-24T19:20:44+09:00
Subject: Re: Inherited & load

On 7/24/07, F. Senault <fred@lacave.net> wrote:
> Le 24 juillet 2007 � 10:02, Robert Dober a �crit :
>
> > On 7/24/07, F. Senault <fred@lacave.net> wrote:
> >> Is there a trick somewhere that would allow me to trigger the inherited
> >> method at each time the file containing the "sub-class" (e.g. Test2) is
> >> loaded ?
> > As Todd pointed out already, "inheritance" will happen only once,
> > might it be that you have  chosen a suboptimal mechanism ;) for what
> > you want to achieve?
> > Maybe you could tell us a little bit more about that?
>
> The full code is there :
>
> http://www.lacave.net/~fred/projets/plugin.rb
>
> It's working behind the scenes in this project :
>
> http://talisker.lacave.net/news/ngraph/
>
> Basically, I have a Plugin class, which implements a few methods,
> including at the class level.
>
> Then, I reuse this class in a few projects, by inheriting it in a base
> class.  For instance, I can write :
>
> class Tester < Plugin
>   plugin_must_implement :register
>   plugin_must_implement :getdata
>   plugin_load_glob "./testers/[a-zA-Z0-9].rb"
>   # methods
> end
>
> Then, when I use Tester.load!, all the files in the specified path are
> load'ed, and all the classes inheriting from Tester are registered as
> plugins of that class, validated against the obligatory methods, and,
> unless told otherwise, an instance of each is created and made available
> and enumerable through an array.
I do not see any particular reason why not to use Module inclusion;
Instead of
class Tester < Plugin
class Tester
   include Plugin ## or maybe extend, I have not looked into the details
end
Now you can be sure that
Plugin#included / Plugin#extended
is executed evry time you load a file.
Did I miss something?
Oh yes of course might be a pain to redesign :(.

Cheers
Robert
Then, I can use, for instance :
>
> Tester.each do |t|
>   t.register
>   d = t.getdata
>   # process the tester data
> end
>
> In the concrete case of my newsserver, I collect data to make the graphs
> from different sources.  So, when I have new data, instead of modifying
> the main body of the grapher program, I can add a new plugin in a small
> rb file (averaging 25 lines) and it's "magically" taken into account...
>
> I've already managed to reuse this class in at least four different
> projects, and I kind of like the concept...  :)
>
> Now, in the event of a long running process, I would like to "hotplug"
> the plugins, and, so, be able to simply reload everything.  My problem
> is that I don't see how I can find the classes contained in a file I
> just loaded without playing with inherited / Object.constants.
>
> My current working idea is this one :
>
> #! /usr/local/bin/ruby
>
> #module Toto
> class Test
>   class <<self
>     attr_accessor :loaded_classes
>     def do_load
>       @loaded_classes ||= {}
>       [ "test2.rb", "test3.rb" ].each do |f|
>         o = Object.constants
>         load f
>         ( Object.constants - o ).each do |c|
>           t = Object.const_get(c)
>           if t.is_a? Class then
>             if t.superclass == Test then
>               @loaded_classes[f] ||= []
>               @loaded_classes[f] << t
>             end
>           end
>         end
>       end
>     end
>   end
> end
>
> Test.do_load
> p Test.loaded_classes
> Test.do_load
> p Test.loaded_classes
>
> Needless to say, I still believe inherited was a bit simpler...  :)
>
> (And it doesn't cope with classes being suppressed.)
>
> Fred
> --
> Au bout  De la course  Remonte jusqu'a  A la source  One trip  One noise
> Circuit  Nuit bleue  Sp�cialiste  De l'enjeu         One trip  One noise
> Longue attente avant de s'elancer  One trip                 (Noir D�sir,
> Longue vie et tout a recracher     One noise      One Trip / One Noise)
>
>


-- 
I always knew that one day Smalltalk would replace Java.
I just didn't know it would be called Ruby
-- Kent Beck