I think that instead of a "base" class that will be overriden to support another media it will be better to create a class that, during creation, accepts a "helper" class that implements the I/O scheme.

package ShoppingCart;

sub new {
  my $class = shift;
  my $self = {};
  bless $self, $class;
  $self->initialize(@_);
  return $self;
}
sub initialize {
  my $self = shift;
  $self->{IO} = shift;
}

sub PrintAll {
  my $self = shift;
  while (my $item = $self->{IO}->GetNext()) {
    ...
  }
}
...

package ShoppingCart::IO::File;
# this is NOT a subclass of ShoppingCart!!!
sub new { ... }
sub GetNext {}
sub ResetCounter {}
...

package ShoppingCart::IO::DBI;
sub new { ... }
sub GetNext {}
sub ResetCounter {}
...

package main;

my $IO = new ShoppingCart::IO::DBI $server, $username, $password;
my $Cart = new ShoppingCart $IO;
...

[download]

There might be some inheritance between the IO Scheme implementation objects, but I doubt it.

Also ... if you really really cared you could add some code to ShoppingCart::initilize() that would test whether the passed IOScheme object supports all the required methods with $IO->can(...).

I do not know if this will be of any help in your case though.

  Jenda

In reply to Re: OOP: Plugin Style Development by Jenda
in thread OOP: Plugin Style Development by jk2addict

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