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Inherit parent, AND also import parent's exported sub ??

by exilepanda (Pilgrim)
on Sep 08, 2016 at 15:21 UTC ( #1171402=perlquestion: print w/replies, xml ) Need Help??

exilepanda has asked for the wisdom of the Perl Monks concerning the following question:

I can use parent 'Some::Class' to sub class a parent class, but the parent class' exported sub won't import, or say parent take that sub as a method and I can only call that in OO way (but it crash that sub's @_ sequence for sure).

Is that anyway I can sub class a class and also have the parent class' functions back too? Thanks in advance!

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Re: Inherit parent, AND also import parent's exported sub ??
by stevieb (Canon) on Sep 08, 2016 at 15:33 UTC

    You can do this by using the SUPER pseudo-class. Here's an example:

    use warnings; use strict; package One; sub foo { print "I'm One::foo()\n"; } package Two; use base 'One'; sub new { return bless {}, shift; } sub foo { my $self = shift; print "I'm Two::foo(). I'm going to call " . "my Parent's foo()...\n"; $self->SUPER::foo(); } package main; my $obj = Two->new; $obj->foo();

    Output:

    I'm Two::foo(). I'm going to call my Parent's foo()... I'm One::foo()

    See perlobj.

      Umm.. sorry perhaps I didn't make my question clear enough. But take your sample as an example:
      use warnings; use strict; package One; require Exporter; # added our @ISA =qw/Exporter/;# added our @EXPORT = qw/foo/;# added sub foo { print "I'm One::foo >> @_ \n"; # changed } package Two; use base 'One'; sub new { return bless {}, shift; } sub foo { my $self = shift; print "I'm Two::foo(). I'm going to call " . "my Parent's foo()...\n"; $self->SUPER::foo(); } package main; my $obj = Two->new; $obj->foo("abc"); # Now foo() has an extra first element in @_ foo("abc"); # die() for Bareword from 'strict subs'
      In this case foo() was not created/designed as a method in One, but an exported function. From my understanding, foo() is only visible in Two, but not main::. Actually, I can do that like :
      package Two; use base 'One'; require Exporter; our @EXPORT = qw/foo/; *foo = \&One::foo; sub new { ... } sub newMethod { ... } sub overrideOldMethod { ... }
      But then, I have to declare every function from the base class manually, and if I sub class Two later, I have to do that again. So, is that anyway I can having both inherit the base class (methods), and also have their exported functions at once?

        Read Exporter

        use base 'One'; use One '/.+/';

        OO classes that export lots of stuff ... code smell :)

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