From: Robert Klemme <lists@...>
Date: 2012-08-24T18:46:56+09:00
Subject: Re: Would you merge repeating code even when it gets more complex?

Martin J. wrote in post #1073029:
> Hi, I wrote a module including some instance and class methods with are
> very similar. That means some lines do exactly the same once for
> instance and once for class methods. I started to refactor theses
> methods but the code got quite complex as a result.
>
> Please take a look at this module:
>
> https://github.com/mjio/uberhook/blob/master/lib/uberhook/base.rb#L43
>
> Would you merge these methods to remove the repeating code even when the
> code gets more complex and harder to read?

I haven't looked to thoroughly but for example this calls for
simplification:

      def run_instance_callback(type, target, scope)
        return unless instance_hooks[target].has_key?(type)
        scope.instance_eval(&instance_hooks[target][type])
      end

      def run_class_callback(type, target, scope)
        return unless class_hooks[target].has_key?(type)
        scope.instance_eval(&class_hooks[target][type])
      end

->

      def self.run_callback(type, target, scope, hooks)
        return unless hooks[target].has_key?(type)
        scope.instance_eval(&hooks[target][type])
      end

->

      def self.run_callback(type, target, scope, hooks)
        tp = hooks[target][type] and scope.instance_eval(&tp)
      end

Looking a bit further it seems you want to put this in a class
hierarchy:
Hooks
ClassHooks < Hooks
InstanceHooks < Hooks

Then apply "template method pattern" e.g. for the different conditions
in method instance_hook and class_hook.

Pushing this further you then only retain method instance_hooks and
class_hooks which return a class of the corresponding type.  Instead
calling instance_hook(...) {|..|} someone will invoke
instance_hooks.hook(...) {|...|}.  You could as well keep instance_hook
but create forwarding in a simple way, e.g.

%w{hook process_method_added}.each do |name|
  %w{class instance}.each do |scop|
    class_eval "def #{scope}_#{name}(*a,&b) 
#{scope}_hooks.#{name}(*a,&b) end"
  end
end

Kind regards

robert

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