/ 
accessors-1.01
River stage two • 16 direct dependents • 48 total dependents
/ accessors

NAME

accessors - create accessor methods in caller's package.

SYNOPSIS

package Foo;
use accessors qw( foo bar baz );

my $obj = bless {}, 'Foo';

# generates chaining accessors
# that you can set like this:
$obj->foo( 'hello ' )
    ->bar( 'world' )
    ->baz( "!\n" );

# you get the values by passing no params:
print $obj->foo, $obj->bar, $obj->baz;

DESCRIPTION

The accessors pragma lets you create simple accessors at compile-time.

This saves you from writing them by hand, which tends to result in cut-n-paste errors and a mess of duplicated code. It can also help you reduce the ammount of unwanted direct-variable access that may creep into your codebase when you're feeling lazy. accessors was designed with laziness in mind.

Method-chaining accessors are generated by default. Note that you can still use accessors::chained directly for reasons of backwards compatability.

See accessors::classic for accessors that always return the current value if you don't like method chaining.

GENERATED METHODS

accessors will generate methods that return the current object on set:

sub foo {
    my $self = shift;
    if (@_) { $self->{-foo} = shift; return $self; }
    else    { return $self->{-foo}; }
}

This way they can be chained together.

Why prepend the dash?

The dash (-) is prepended to the property name for a few reasons:

  • interoperability with Error.

  • to make it difficult to accidentally access the property directly ala:

    use accessors qw( foo );
$obj->{foo};  # prevents this by mistake
$obj->foo;    # when you probably meant this

    (this might sound woolly, but it's easy enough to do).

  • syntactic sugar (this is woolly :).

You shouldn't care too much about how the property is stored anyway - if you do, you're likely trying to do something special (and should really consider writing the accessors out long hand), or it's simply a matter of preference in which case you can use accessors::classic, or sub-class this module.

PERFORMANCE

There is little-to-no performace hit when using generated accessors; in fact there is usually a performance gain.

  • typically 10-30% faster than hard-coded accessors (like the above example).

  • typically 1-15% slower than optimized accessors (less readable).

  • typically a small performance hit at startup (accessors are created at compile-time).

  • uses the same anonymous sub to reduce memory consumption (sometimes by 80%).

See the benchmark tests included with this distribution for more details.

MOTIVATION

The main difference between the accessors pragma and other accessor generators is simplicity.

  • interface

    use accessors qw( ... ) is as easy as it gets.

  • a pragma

    it fits in nicely with the base pragma:

    use base      qw( Some::Class );
use accessors qw( foo bar baz );

    and accessors get created at compile-time.

  • no bells and whistles

    The module is extensible instead.

SUB-CLASSING

If you prefer a different style of accessor or you need to do something more complicated, there's nothing to stop you from sub-classing. It should be pretty easy. Look through accessors::classic, accessors::ro, and accessors::rw to see how it's done.

CAVEATS

Classes using blessed scalarrefs, arrayrefs, etc. are not supported for sake of simplicity. Only hashrefs are supported.

THANKS

Thanks to Michael G. Schwern for indirectly inspiring this module, and for his feedback & suggestions.

Also to Paul Makepeace and David Wright for showing me faster accessors, to chocolateboy for his contributions, the CPAN Testers for their bug reports, and to James Duncan and people on London.pm for their feedback.

AUTHOR

Steve Purkis <spurkis@cpan.org>

SEE ALSO

accessors::classic, accessors::chained

Similar and related modules:

base, fields, Class::Accessor, Class::Struct, Class::Methodmaker, Class::Generate, Class::Class, Class::Tangram, Object::Tiny