From: Geoff Stanley <geoffstanley@...>
Date: 2006-04-27T09:41:34+09:00
Subject: Extending Methods

Hello all.

I'm working on a plugin system for a IRC client I'm currently making. 
The current plan is for plugins to extend the base classes of the 
program. Often a plugin will need to add a little bit of functionality 
to an already existing method in an already existing class.

For example, I've got a logging plugin. I want it to extend the Channel 
class to allow for logging of conversations. It needs to redefine 
Channel's initialize method to open a log file. But it can't eliminate 
all the important things the base initialize method did.

I've thought about doing this with alias, but I haven't succeeded. My 
thoughts were to rename 'initialize' to 'old_initialize', then have the 
plugin redefine 'initialize'. In code:

class Channel
    alias old_initialize initialize
    def initialize
        old_initialize
        # Then write custom code. (To open a log file, for example.)
    end
end

This doesn't work, however, because it leads to a stack overflow. I 
think the reason for the overflow is because, when this is done twice, 
old_initialize will call itself recursively with no end.

Anyone have any ideas for how this could be done? It doesn't have to use 
alias, but the general intention is thus: I want to redefine a method 
and 'copy and paste' the old code from the method into the new method at 
a given point. Sort of like using 'super', but no inheritence required.

Thanks! Responses are greatly appreciated.

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