From: Ehsanul Hoque <ehsanul_g3@...>
Date: 2009-09-22T17:56:19+09:00
Subject: Re: Monkeypatching multiple classes with similar methods

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Hey. You just have a tiny couple of bugs. Try this instead (untested=2C but=
 you get the idea):

[Klass1=2C Klass2=2C Klass3].each do |klass|
  klass.module_eval do
    alias_method :original_meth=2C :meth
    def meth(*stuff=2C &block)
      puts "#{self.class}.meth has been patched"
      original_meth(*stuff=2C &block)
    end
  end
end

> Date: Tue=2C 22 Sep 2009 17:45:06 +0900
> From: lasso@lassoweb.se
> Subject: Monkeypatching multiple classes with similar methods
> To: ruby-talk@ruby-lang.org
>=20
> Hello!
>=20
> I'm trying to monkeypatch a number of related classes that all
> implements the same method (meth). The methods all take one required
> argument (stuff) but some of the individual methods may require more
> arguments (or a block). All I want to do in each call to meth is to
> print some debug data and then pass the incoming arguments to the
> original method. This works great as long as I know the exact number
> of arguments required=2C but when the number of arguments starts to
> change my code breaks badly. Is there any way (in ruby 1.8.7) to
> "copy" the original method signature when defining my own replacement
> method?
>=20
> /lasso
>=20
> --- CODE START ---
> class Klass1
>   def meth(stuff)
>     puts "You've sent #{stuff} to #{self.class}.meth"
>   end
> end
>=20
> class Klass2
>   def meth(stuff=2C &block)
>     block_text =3D block_given? ? 'with' : 'without'
>     puts "You've sent #{stuff} to #{self.class}.meth #{block_text} a
> block"
>   end
> end
>=20
> class Klass3
>   def meth(stuff=2C morestuff)
>     puts "You've sent #{stuff} to #{self.class}.meth"
>   end
> end
>=20
> # Broken monkeypatching. Only works on Klass1
> [Klass1=2C Klass2=2C Klass3].each do |klass|
>   klass.module_eval do
>     alias_method :original_meth=2C :meth
>     def meth(stuff)
>       puts "#{self.class}.meth has been patched"
>       original_meth(stuff)
>     end
>   end
> end
>=20
> Klass1.new.meth('one')
> Klass2.new.meth('two') { 'three' } # Block is not passed after
> monkeypatching
> Klass2.new.meth('four')
> Klass3.new.meth('five'=2C 'six') # Raises ArgumentError after
> monkeypatching
> --- CODE END ---
>=20
 		 	   		  =0A=
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