From: Chris Pine <nemo@...>
Date: 2003-01-04T02:09:11+09:00
Subject: Re: How to call overridden methods (finally!)

----- Original Message -----
From: "ts" <decoux@moulon.inra.fr>

pigeon% cat b.rb
#!./ruby
a = Numeric.instance_method(:to_int)
b = Method.instance_method(:call).bind(a)
b.call
pigeon%

pigeon% b.rb
/b.rb:4:in `call': you cannot call unbound method; bind first (TypeError)
        from ./b.rb:4:in `call'
        from ./b.rb:4
pigeon%


Guy Decoux
----------------------------

Thanks, Guy!  You're a lifesaver.  :)

So this seems more like an argument *for* allowing this into the standard
interpreter.  Currently the above code raises the following exception
instead:

$ ./test.rb
./test.rb:13:in `bind': bind argument must be an instance of Method
(TypeError)
        from ./test.rb:13

Which I think is a less helpful exception.  Is the problem that it is wrong
to `call' something which is a kind_of Method, but not a Method instance?
Or is the problem that `a' is an UnboundMethod?

Still, in the vase majority of cases, calling an overridden parent method
doesn't raise an exception at all... it just does what you want it to do.  I
think that in every case you can achieve the same results by using `super'
in clever ways, but it is messy and requires a lot of aliasing.  Why not
allow us to do the same thing more cleanly?


Chris