Animal Shelter Manager is a complete computersolution for animal sanctuaries, rescue shelters,and veterinary surgery clinics. It featurescomplete animal and owner management, documentgeneration, flexible reporting, charts, InternetWeb site publishing, and more.License: GNU General Public License (GPL)Changes:
This release adds support for OpenOffice 3 andMicrosoft Office 2007 andfinally allows images to be used in generateddocuments. It includessupport for spinner widgets and various UIimprovements/bugfixes, alongwith a SQL console and screen to edit hiddendatabase properties.
Moose::Cookbook::Basics::BinaryTree_BuilderAndLazyBuild(User Contributed Perl DocumentatMoose::Cookbook::Basics::BinaryTree_BuilderAndLazyBuild(3)NAME
Moose::Cookbook::Basics::BinaryTree_BuilderAndLazyBuild - Builder methods and lazy_build
VERSION
version 2.1202
SYNOPSIS
package BinaryTree;
use Moose;
has 'node' => (is => 'rw', isa => 'Any');
has 'parent' => (
is => 'rw',
isa => 'BinaryTree',
predicate => 'has_parent',
weak_ref => 1,
);
has 'left' => (
is => 'rw',
isa => 'BinaryTree',
predicate => 'has_left',
lazy => 1,
builder => '_build_child_tree',
);
has 'right' => (
is => 'rw',
isa => 'BinaryTree',
predicate => 'has_right',
lazy => 1,
builder => '_build_child_tree',
);
before 'right', 'left' => sub {
my ($self, $tree) = @_;
$tree->parent($self) if defined $tree;
};
sub _build_child_tree {
my $self = shift;
return BinaryTree->new( parent => $self );
}
DESCRIPTION
If you've already read Moose::Cookbook::Basics::BinaryTree_AttributeFeatures, then this example should look very familiar. In fact, all
we've done here is replace the attribute's "default" parameter with a "builder".
In this particular case, the "default" and "builder" options act in exactly the same way. When the "left" or "right" attribute is read,
Moose calls the builder method to initialize the attribute.
Note that Moose calls the builder method on the object which has the attribute. Here's an example:
my $tree = BinaryTree->new();
my $left = $tree->left();
When "$tree->left()" is called, Moose calls "$tree->_build_child_tree()" in order to populate the "left" attribute. If we had passed "left"
to the original constructor, the builder would not be called.
There are some differences between "default" and "builder". Notably, a builder is subclassable, and can be composed from a role. See
Moose::Manual::Attributes for more details.
The lazy_build shortcut
The "lazy_build" attribute option can be used as sugar to specify a whole set of attribute options at once:
has 'animal' => (
is => 'ro',
isa => 'Animal',
lazy_build => 1,
);
This is a shorthand for:
has 'animal' => (
is => 'ro',
isa => 'Animal',
required => 1,
lazy => 1,
builder => '_build_animal',
predicate => 'has_animal',
clearer => 'clear_animal',
);
If your attribute starts with an underscore, Moose is smart and will do the right thing with the "predicate" and "clearer", making them
both start with an underscore. The "builder" method always starts with an underscore.
You can read more about "lazy_build" in Moose::Meta::Attribute
CONCLUSION
The "builder" option is a more OO-friendly version of the "default" functionality. It also separates the default-generating code into a
well-defined method. Sprinkling your attribute definitions with anonymous subroutines can be quite ugly and hard to follow.
AUTHORS
o Stevan Little <stevan.little@iinteractive.com>
o Dave Rolsky <autarch@urth.org>
o Jesse Luehrs <doy@tozt.net>
o Shawn M Moore <code@sartak.org>
o XXXX XXX'XX (Yuval Kogman) <nothingmuch@woobling.org>
o Karen Etheridge <ether@cpan.org>
o Florian Ragwitz <rafl@debian.org>
o Hans Dieter Pearcey <hdp@weftsoar.net>
o Chris Prather <chris@prather.org>
o Matt S Trout <mst@shadowcat.co.uk>
COPYRIGHT AND LICENSE
This software is copyright (c) 2006 by Infinity Interactive, Inc..
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
perl v5.18.2 2014-01-19 Moose::Cookbook::Basics::BinaryTree_BuilderAndLazyBuild(3)