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in reply to Re: goto superclass method
in thread goto superclass method

This is an infinite loop
It's an infinite loop, but not for the reasons you state. SUPER:: is always relative to __PACKAGE__, and when you start saying sub Foo::bar, the __PACKAGE__ doesn't change to Foo, so you have a problem with SUPER.

In short, Don't Do That. Properly written code works properly: 

package Base;
sub do_me {
  my $self = shift;
  print "Base do_me\n";
}
package Derived;
@ISA = qw(Base);
sub do_me {
  my ($self) = @_; # no shift, so we can goto
  print "About to jump...\n";
  goto &{$self->can("SUPER::do_me")};
}
package main;
Derived->do_me;

[download]

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

Replies are listed 'Best First'.
Re^3: goto superclass method
by Aristotle (Chancellor) on Dec 22, 2004 at 21:49 UTC

    SUPER:: is always relative to __PACKAGE__, and when you start saying sub Foo::bar, the __PACKAGE__ doesn't change to Foo, so you have a problem with SUPER.

    That's wrong.

    #!/usr/bin/perl
use strict;
use warnings;

package Foo;
sub bar { }

package Baz;
our @ISA = qw( Foo );
sub bar {
    my $self = shift;
    print $self->SUPER::can( "bar" ), "\n";
    print $self->can( "SUPER::bar" ), "\n";
};

package main;

print UNIVERSAL::can( Baz => "bar" ), "\n";

Baz->bar;

__END__
CODE(0x815a230)
CODE(0x815a230)
CODE(0x813bc4c)

    [download]

    Interestingly enough, I thought I had tried the $self->can( "SUPER::foo" ) combination, but apparently I didn't. Huh.

    Makeshifts last the longest.

[reply]
[d/l]
      Huh? Your example shows that both UNIVERSAL::can and SUPER::can on asking how a "Baz" can "bar" return the same code (which is Baz::bar), and that SUPER::bar for Baz is in fact the one in Foo::bar.

      That's exactly what I said. You didn't show "wrong" on anything. Did you mean something else?

      -- Randal L. Schwartz, Perl hacker
      Be sure to read my standard disclaimer if this is a reply.

[reply]

        You claimed the current __PACKAGE__ affects the result of Foo->SUPER::can( 'bar' ):

        when you start saying sub Foo::bar, the __PACKAGE__ doesn't change to Foo, so you have a problem with SUPER.

        I posted code where changing packages, and thus __PACKAGE__, is inconsequential, contrary to your claim.

        So the reasoning in my initial post about why the goto there is an infinite loop is correct.

        Makeshifts last the longest.

[reply]
Re^3: goto superclass method
by steves (Curate) on Dec 22, 2004 at 21:41 UTC

    merlyn shows that it takes a wizard to arrive at the purest form of perverted code.

    Thanks. Now let's all wash our hands. Twice for good measure.

[reply]

      I didn't find this perverted at all. What that says about me is your guess. :-)

      Makeshifts last the longest.

[reply]
Re^3: goto superclass method
by Mr. Muskrat (Canon) on Dec 22, 2004 at 22:00 UTC

    What's wrong with leaving &Derived::do_me out altogether?

    package Base;
sub do_me {
  my $self = shift;
  print "Base do_me\n";
}

package Derived;
@ISA = qw(Base);

package main;
Derived->do_me;

    [download]

    It doesn't use goto but the result is the same as far as I can tell.

    Update: Okay, ignore me. I got distracted from the original question of how to conditionally jump to a super class.

[reply]
[d/l]

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