Perl OO Question, Inheritance - calling parent method

Question

Why am I not able to call testmethod of parent using child object in the following code?

use strict;
use Data::Dumper;

my $a = C::Main->new('Email');
$a->testmethod();

package C::Main;


sub new {
    my $class = shift;
    my $type  = shift;
    $class .= "::" . $type;
    my $fmgr = bless {}, $class;
    $fmgr->init(@_);
    return $fmgr;
}

sub init {
    my $fmgr = shift;
    $fmgr;
}

sub testmethod {
    print "SSS";
}

package C::Main::Email;
use Net::FTP;

@C::Main::Email::ISA = qw( C::Main );

sub init {
    my $fmgr = shift;
    my $ftp = $fmgr->{ftp} = Net::FTP->new( $_[0] );
    $fmgr;
}

package C::Main::FTP;
use strict;
use Net::FTP;

@C::Main::Email::FTP = qw( C::Main );

sub init {
    my $fmgr = shift;
    $fmgr;
}

You don't need to keep repeating use strict; in each package. Since strict is a lexically scoped pragma, it is in effect until the current scope ends. Package declarations do not create a scope, so if use strict; is placed at the top of a file, it is in scope for the entire file. — Eric Strom
– Eric Strom, Commented Mar 2, 2011 at 21:40

bvr · Accepted Answer · 2011-03-02 21:29:41Z

5

It is because assignment into @ISA is done at runtime, thus after you try to call the method.

You can make it work by surrounding by BEGIN, moving it to compile time:

BEGIN { our @ISA = qw( C::Main ) }

or you can do

use base qw( C::Main );

which is also done in compile time. Both variants do fix your problem.

answered Mar 2, 2011 at 21:29

bvr

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2 Comments

Joel Berger Over a year ago

I concur, however, from what I read, use parent ... is now preferred over use base ....

bvr Over a year ago

@Joel - I heard that base has some problems and somehow is trying to solve too much, although I never used it for anything else than inheritance. parent also came core in 5.10.1, at least according to Module::CoreList.

Christopher Biggs · Accepted Answer · 2011-03-03 00:13:49Z

0

If you're writing new OO code in Perl, use Moose!

Returning to 'use base' after having used Moose is like going back to the 1950s.

answered Mar 3, 2011 at 0:13

Christopher Biggs

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