From: Damphyr <damphyr@...>
Date: 2003-04-04T08:25:25+09:00
Subject: Plugins (sort off)

Well I *am* new to Ruby, been playing around for about three weeks now 
(well, whenever I can think after work anyway) and while playing around 
I put together a very primitive (in my opinion) way of making plugins.
Well calling it plugins probably is the wrong thing to do - let's say 
that I like distributing my code in small files all over the place 
because I hate scrolling and I like putting it together again 
programmatically.
It was usefull for what I'm building (a dyndns refresh utility) but I 
want to ask for your ideas on how to do this better (especially on 
clean-up).
Here's the deal:

By convention I define a directory (say ./lib, where . is the 
installation directory of the app - find me a way to always calculate it 
correctly - wherever the script is called - and I will be happy) where I 
dump my "plugins".
What the so called "plugin" is, is actually a file (with a 
pick-and-choose extension, call it .module) with Ruby code in it.
Needs to be well formed, and not be a class or module definition (I'm 
not sure about that, I haven't tried it actually).
What I actually do, is define a method in there like this:

def detect()
	#some really nifty stuff
end

In the actual app I read all files in the ./lib directory with a .module 
extension and use the filenames as the "plugin" names.
So each file is a way of detection (to use the semantics of my utility) 
that defines a detect() method and in the app I have a method that reads 
the file and builds a module out of it.

def address(methodname)
    #blabla
    #construct the full pathname to the module file (fullname)
    if @methods.include?(fullname)
#@methods is just an array where the contents of ./lib were read
       cntnt=IO.readlines(fullname).join
       IPDetector.module_eval(cntnt)#IPDetector is the app
       rtrn = detect()
    else
       raise IPDetectorError,"Unsupported method \"#{methodname}\"!"
    end
    return rtrn
end

Now, this works, but if I call address a couple of times with the 
different methods I'll end up with a couple of anonymous modules.
Is there any way to clean them up? Some way to remove a mixin from a 
class? From what I saw in Module the method I would use ( 
Module#remove_method ) is private so no cleaning up.
It would be nice to find a way to remove the module - then I can define 
constants in the module file without fear of redefinitions.
(Should not forget: I'm still using Ruby 1.6.8)
This whole thing is rather slow - but some kind of module pooling can be 
done if I use an empty class (just like in the module_eval example ) for 
every module file and keep them around, tracking which modules have been 
created.
Any comments?
V.-



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