Objects, Modules and Packages

Package basics

A package is a collection of methods
Lives in its own namespace
Package methods can be exported or called directly
- Foo::bar()
- Foo->bar()
- bar() (if Foo exports it)

Module basics

A module is a file containing one or more packages
Most people use "module" and "package" interchangably

Object basics

An object is a blessed reference to a hash
- It doesn't have to be a hash reference, but it's most common.
Blessing assigns a single class to an object
An object can be re-blessed
You can muck with the internals, but that doesn't mean you should

1;

Modules must end with a true value
It doesn't have to be 1
Packages don't have the same restriction

Perl's object inheritance methods use @ISA to determine what classes a module inherits from. Years ago, inheritance was declared by modifying @ISA directly; now, most programs use the base pragma to declare inheritance.

The following are mostly equivalent:

    package Foo;
    require Wango;
    @ISA = ( "Wango" );

    package Foo;
    use base "Wango";

Want to contribute?

Submit a PR to github.com/petdance/perl101