[Xotcl] Unforwarding object method

From: Scott Gargash <scottg_at_atc.creative.com>
Date: Tue, 7 Mar 2006 14:43:17 -0700

Hello,

I've just started looking at XOTcl over the last couple days, and so far I like it a lot. Since I'm
still learning, I assume I've overlooked something in the documentation, but I can't find how to
remove a forwarded method from an object. It seems that all I can do is add a forwarded method, but
once installed, I can never unforward a method. Is this true?

Here's an (simplified) example of what I'm trying to do:

Object a
a proc foo {args} {
  puts "a: [self] foo"
}

Object b
b set overrides {}
b proc foo {obj} {
  puts "b: [self] foo"
  if {-1 == [lsearch [my set overrides] $obj]} {
    puts "b is overriding $obj foo"
    $obj forward foo [self] overridefoo $obj
  }
}

b proc overridefoo {obj args} {
  if {$args eq "done"} {
    puts "stop forwarding foo for $obj"
    set idx [lsearch -exact [my set overrides] $obj]
    my set overrides [lreplace [my set overrides] $idx $idx]
    # This doesn't work! What should be here?
    $obj forward foo {}
    puts "redispatching foo to native $obj foo"
    $obj foo $args
  } else {
    puts "using override of foo on $obj $args"
  }
}
a foo 123
b foo a
a foo 234
a foo done

----------

>From what I gather, the intended mechanism for doing this is to use a mixin to intercept the foo
method, but a already has a foo method that's being used for other purposes. I suppose I could
dynamically create another object (or would it have to be a class?) to use as a mixin, but that
seems unnecessarily complex. Is there a better way to accomplish what I'm trying to do?


BTW, I'm running xotcl 1.3.6. If I run the above sample 3 times, I get the following error:

procedure "foo" has formal parameter "::xotcl::initProcNS" that is not a simple name

and the interpreter crashes on the next command. That's probably a bug, but since I'm not at the
latest release, I don't know if it's something that's been fixed already.

Thanks.

      Scott




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