perl - Objects, Modules and Packages

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

@ISA

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";


source: http://perl101.org/objects.html