in reply to Interfaces

You could create an abstract class where each method prints an error, like so: 
package AbstractClass;
sub new {
    my($class) = shift;
    bless {
        "classVar1" => undef,
        "classVar2" => undef
    }, $class;
}
sub methodOne {
    print "Error: Use of undefined Abstract Method\n";
}
sub methodTwo {
    print "Error: Use of undefined Abstract Method\n";
}

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and then override the methods in the subclasses: 
package SomeObject;
@ISA = ("AbstractClass");
sub methodOne {
    print "Doing the real function\n";
}

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that's very basic code...would it do something like what you want?

Replies are listed 'Best First'.
RE: Re: Interfaces
by btrott (Parson) on Jun 07, 2000 at 03:16 UTC
    Since you're writing a bunch of subroutines that do the same thing, you can be lazy and just alias them: 
        sub cant_do_that {
        my $self = shift;
        print "Error: Use of undefined Abstract Method by $self.\n";
    }

    use subs qw/methodOne methodTwo/;
    *methodOne = \&cant_do_that;
    *methodTwo = \&cant_do_that;

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[d/l]
      Thus saith btrott: 
      sub cant_do_that { 
        my $self = shift; 
        print "Error: Use of undefined Abstract Method by $self.\n"; 
    } 
 
    use subs qw/methodOne methodTwo/; 
    *methodOne = \&cant_do_that; 
    *methodTwo = \&cant_do_that;

      [download]
      I'd simplify the whole lot of that by doing what use subs does directly: 
      BEGIN {
  for my $fakir (qw(methodOne methodTwo)) {
    *$fakir = sub { die "undef abstract method $fakir used by ".(shift
+); }
  }
}

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      No fuss, no muss, and you even get a distinguishing mark.

      -- Randal L. Schwartz, Perl hacker

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[d/l]
[select]
        merlyn: 
        BEGIN {
  for my $fakir (qw(methodOne methodTwo)) {
    *$fakir = sub { die "undef abstract method $fakir used by ".(shift
+); }
  }
}

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        causes an error with use strict; (Can't use string ("foo") as a symbol ref) and i needed to add 
        no strict 'refs';

        [download]
        inside the BEGIN:...is there a better way?

        --
        michael d. ivey, ivey@gweezlebur.com

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[d/l]
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RE: Re: Interfaces
by chromatic (Archbishop) on Jun 07, 2000 at 03:01 UTC
    I've done something exactly like that. There is one additional bit in my code, though. 
    sub methodOne {
    my $self = shift;
    print "Error:  Use of undefined Abstract Method by $self\n";
}

    [download]
    That way, you know exactly which subclass isn't overriding it.
[reply]
[d/l]

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