NAME

Class::Tiny - Minimalist class construction

VERSION

version 0.002

SYNOPSIS

In Person.pm:

  package Person;

  use Class::Tiny qw( name );

  1;

In Employee.pm:

  package Employee;
  use parent 'Person';

  use Class::Tiny qw( ssn );

  1;

In example.pl:

  use Employee;

  my $obj = Employee->new( name => "Larry", ssn => "111-22-3333" );

  # unknown attributes are fatal:
  eval { Employee->new( name => "Larry", OS => "Linux" ) };
  die "Error creating Employee: $@" if $@;

DESCRIPTION

This module offers a minimalist class construction kit in under 100 lines of code. Here is a list of features:

• defines attributes via import arguments

• generates read-write accessors

• supports custom accessors

• superclass provides a standard new constructor

• new takes a hash reference or list of key/value pairs

• new throws an error for unknown attributes

• new calls BUILD for each class from parent to child

• superclass provides a DESTROY method

• DESTROY calls DEMOLISH for each class from child to parent

It uses no non-core modules (except on Perls older than 5.10, where it requires MRO::Compat from CPAN).

Why this instead of Object::Tiny or Class::Accessor or something else?

I wanted something so simple that it could potentially be used by core Perl modules I help maintain (or hope to write), most of which either use Class::Struct or roll-their-own OO framework each time.

Object::Tiny and Object::Tiny::RW were close to what I wanted, but lacking some features I deemed necessary, and their maintainers have an even more strict philosophy against feature creep than I have.

Compared to everything else, this is smaller in implementation and simpler in API. (The only API is a list of attributes!)

I looked for something like it on CPAN, but after checking a dozen class creators I realized I could implement it exactly how I wanted faster than I could search CPAN for something merely sufficient.

USAGE

Defining attributes

Define attributes as a list of import arguments:

    package Foo::Bar;

    use Class::Tiny qw(
        name
        id
        height
        weight
    );

For each item, a read-write accessor is created unless a subroutine of that name already exists:

    $obj->name;               # getter
    $obj->name( "John Doe" ); # setter

Attribute names must be valid subroutine identifiers or an exception will be thrown.

To make your own custom accessors, just pre-declare the method name before loading Class::Tiny:

    package Foo::Bar;

    use subs 'id';

    use Class::Tiny qw( name id );

    sub id { ... }

By declaring id also with Class::Tiny, you include it in the list of allowed constructor parameters.

Class::Tiny is your base class

If your class does not already inherit from some class, then Class::Tiny will be added to your @ISA to provide new and DESTROY. (The superclass import method will silently do nothing for subclasses.)

If your class does inherit from something, then no additional inheritance is set up. If the parent subclasses Class::Tiny, then all is well. If not, then you'll get accessors set up but no constructor or destructor. Don't do that unless you really have a special need for it.

Define subclasses as normal. It's best to define them with base, parent or superclass before defining attributes with Class::Tiny so the @ISA array is already populated at compile-time:

    package Foo::Bar::More;

    use parent 'Foo::Bar';

    use Class::Tiny qw( shoe_size );

Object construction

If your class inherits from Class::Tiny (as it should if you followed the advice above), it provides the new constructor for you.

Objects can be created with attributes given as a hash reference or as a list of key/value pairs:

    $obj = Foo::Bar->new( name => "David" );

    $obj = Foo::Bar->new( { name => "David" } );

If a reference is passed as a single argument, it must be able to be dereferenced as a hash or an exception is thrown. A shallow copy is made of the reference provided.

BUILD

If your class or any superclass defines a BUILD method, they will be called by the constructor from the furthest parent class down to the child class after the object has been created. No arguments are provided and the return value is ignored. Use them for validation or setting default values.

    sub BUILD {
        my $self = shift;
        $self->foo(42) unless defined $self->foo;
        croak "Foo must be non-negative" if $self->foo < 0;
    }

DEMOLISH

Class::Tiny provides a DESTROY method. If your class or any superclass defines a DEMOLISH method, they will be called from the child class to the furthest parent class during object destruction. No arguments are provided. Return values and errors are ignored.

    sub DEMOLISH {
        my $self = shift;
        $self->cleanup();
    }

SUPPORT

Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker at https://github.com/dagolden/class-tiny/issues. You will be notified automatically of any progress on your issue.

Source Code

This is open source software. The code repository is available for public review and contribution under the terms of the license.

https://github.com/dagolden/class-tiny

  git clone git://github.com/dagolden/class-tiny.git

AUTHOR

David Golden <dagolden@cpan.org>

CONTRIBUTORS

• Karen Etheridge <ether@cpan.org>

• Olivier Mengu� <dolmen@cpan.org>

COPYRIGHT AND LICENSE

This software is Copyright (c) 2013 by David Golden.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004

cpanm Class::Tiny

perl -MCPAN -e shell
install Class::Tiny