From: Rune Hammersland <rune@...>
Date: 2006-11-01T04:56:00+09:00
Subject: Re: Difference between define_method and def method; end

On 31. okt. 2006, at 17:10, ara.t.howard@noaa.gov wrote:
> On Tue, 31 Oct 2006, Rune Hammersland wrote:
>> # Try to redefine method and call super.
>> class Child < Parent
>
> you are not redefining the method here, you are redefining the class.
> if you simply redefine the method it does what you expect:
>
>     harp:~ > cat a.rb
>     class Parent
>        def lol() puts "P: LOL" end
>     end
>
>     class Child < Parent
>        def lol() puts "C: LOL" end
>     end
>
>     c = Child.new
>     Child.class_eval { undef_method :lol }
>
>     class Child  #< Parent
>        def lol
>          print "LOL: "
>          super
>        rescue NameError => e
>            puts e.to_s
>        end
>     end
>
>     c.lol
>
>     harp:~ > ruby a.rb
>     LOL: superclass method `lol' disabled

That is actually the same output I had. My problem (and excuse me for  
not
stating it clearly) is that if I use define_method after undef_method:

     Child.class_eval { undef_method :lol }
     c.lol # raises exception (of course)

     class Child; def lol() print "LOL: "; super end; end
     c.lol # raises exception (superclass method disabled)

     Child.class_eval { define_method(:lol) { print "LOL: "; super } }
     c.lol # prints "LOL: P: LOL"

So you see: defining the method using the def ... end block raises an
exception if you call super after the method has been undefined, while
defining it using define_method does not. I expected it to either  
raise or not
raise the exception in both cases (but do the same for both).

I hope that clarified it (although I'm not sure it did, as explaining  
things
can be hard to do even in your native language).

... or am I still redefining the class using the class ... end block?

-- 
Vennlig Hilsen / Regards
Rune Hammersland