From: Andrew Johnson <ajohnson@...>
Date: 2004-10-01T05:20:01+09:00
Subject: Re: Calling super methods


On Thu, 30 Sep 2004 13:02:58 -0400, Grzegorz Dostatni
<grzegorz@ee.ualberta.ca> wrote:
> 
> Is it possible to call a method of a superclass? Let's say I have a
> instance of class Bar ( subclassed from Foo).
> Both Foo and Bar define a function h()
> 
> I want to call a.h() and have it go the Foo's implementation if it,
> without going through the super() call (ie. do it from outside the
> object).
> 
> I have a code in python that does it:
> 
> class Foo:
> 	def h(self):
> 		print "Foo"
> 
> class Bar(Foo):
> 	def h(self):
> 		print "Bar"
> 
> b = Bar()
> 
> b.h()
>>> prints out "Bar"
> Foo.h(b)
>>> prints out "Foo"

Perhaps there's a shorter call sequence, but ...

class Foo
  def h; puts "foo";end
end
class Bar < Foo
  def h; puts "bar";end
end

a = Bar.new
a.h                                                  #=> 'bar'

## hardcode the call-up class:
Foo.instance_method(:h).bind(a).call                 #=> 'foo'

## more dynamic call-up:
a.class.superclass.instance_method(:h).bind(a).call  #=> 'foo'

## Or, add dynamic call_up to the Object class:
class Object
  def supercede(meth)
    self.class.superclass.instance_method(meth).bind(self).call
  end
  alias :call_up :supercede
end

a.h                                                  #=> 'bar'
a.supercede(:h)                                      #=> 'foo'
a.call_up(:h)                                        #=> 'foo'
__END__

-- 
Andrew L. Johnson   http://www.siaris.net/
      They're not soaking, they're rusting!
          -- my wife (on my dishwashing habits)