Question

How do I apply ‘use base’ in Perl to inherit subs from some base module?

I’m used to C++ inheritance mechanics, and all the sites I googled for this caused more confusion then help. I want to do something like the following:

#! /usr/bin/perl #The base class to inherit from use strict; use warnings;  package 'TestBase';  #------------------------------- sub tbSub {     my ($self, $parm) = @_;     print '\nTestBase: $parm\n'; }  1; 

.

#! /usr/bin/perl #The descendent class use strict; use warnings;  use base qw(TestBase); sub main; sub mySub;  #------------------------------- #Entry point... main();  #---code------------------------ sub main {     mySub(1);     tbSub(2);     mySub(3); }  #------------------------------- sub mySub {     my $parm = shift;     print '\nTester: $parm\n'; } 

Perl complains/cannot find tbSub.

Answer 1

The C++ mechnics aren’t much different than the Perl mechanics: To use inheritance, you need two classes: the base class and the inheriting class. But you don’t have any descendent class.

You are also lacking a constructor. Unlike C++, Perl will not provide a default constructor for you.

Your base class contains a bad syntax error, so I guess you didn’t try the code before posting.

Finally, as tsee already observed, you will have to let Perl know whether you want a function call or a method call.

What you really want would look something like this:

my $foo = TestDescendent->new(); $foo->main();   package TestBase;  sub new {    my $class = shift;    return bless {}, $class; }  sub tbSub {    my ($self, $parm) = @_;    print '\nTestBase: $parm\n'; }  package TestDescendent; use base 'TestBase';  sub main {     my $self = shift;     $self->mySub( 1 );     $self->tbSub( 2 );     $self->mySub( 3 ); }  sub mySub {     my $self = shift;     my $parm = shift;     print '\nTester: $parm\n'; }  1;