trusty (3) MooseX::AttributeShortcuts.3pm.gz
NAME
MooseX::AttributeShortcuts - Shorthand for common attribute options
VERSION
This document describes version 0.022 of MooseX::AttributeShortcuts - released September 29, 2013 as part
of MooseX-AttributeShortcuts.
SYNOPSIS
package Some::Class;
use Moose;
use MooseX::AttributeShortcuts;
# same as:
# is => 'ro', lazy => 1, builder => '_build_foo'
has foo => (is => 'lazy');
# same as: is => 'ro', writer => '_set_foo'
has foo => (is => 'rwp');
# same as: is => 'ro', builder => '_build_bar'
has bar => (is => 'ro', builder => 1);
# same as: is => 'ro', clearer => 'clear_bar'
has bar => (is => 'ro', clearer => 1);
# same as: is => 'ro', predicate => 'has_bar'
has bar => (is => 'ro', predicate => 1);
# works as you'd expect for "private": predicate => '_has_bar'
has _bar => (is => 'ro', predicate => 1);
# extending? Use the "Shortcuts" trait alias
extends 'Some::OtherClass';
has '+bar' => (traits => [Shortcuts], builder => 1, ...);
# or...
package Some::Other::Class;
use Moose;
use MooseX::AttributeShortcuts -writer_prefix => '_';
# same as: is => 'ro', writer => '_foo'
has foo => (is => 'rwp');
DESCRIPTION
Ever find yourself repeatedly specifying writers and builders, because there's no good shortcut to
specifying them? Sometimes you want an attribute to have a read-only public interface, but a private
writer. And wouldn't it be easier to just say "builder => 1" and have the attribute construct the
canonical "_build_$name" builder name for you?
This package causes an attribute trait to be applied to all attributes defined to the using class. This
trait extends the attribute option processing to handle the above variations.
USAGE
This package automatically applies an attribute metaclass trait. Unless you want to change the defaults,
you can ignore the talk about "prefixes" below.
EXTENDING A CLASS
If you're extending a class and trying to extend its attributes as well, you'll find out that the trait
is only applied to attributes defined locally in the class. This package exports a trait shortcut
function "Shortcuts" that will help you apply this to the extended attribute:
has '+something' => (traits => [Shortcuts], ...);
PREFIXES
We accept two parameters on the use of this module; they impact how builders and writers are named.
-writer_prefix
use MooseX::::AttributeShortcuts -writer_prefix => 'prefix';
The default writer prefix is '_set_'. If you'd prefer it to be something else (say, '_'), this is where
you'd do that.
-builder_prefix
use MooseX::::AttributeShortcuts -builder_prefix => 'prefix';
The default builder prefix is '_build_', as this is what lazy_build does, and what people in general
recognize as build methods.
NEW ATTRIBUTE OPTIONS
Unless specified here, all options defined by Moose::Meta::Attribute and Class::MOP::Attribute remain
unchanged.
Want to see additional options? Ask, or better yet, fork on GitHub and send a pull request. If the
shortcuts you're asking for already exist in Moo or Mouse or elsewhere, please note that as it will carry
significant weight.
For the following, "$name" should be read as the attribute name; and the various prefixes should be read
using the defaults.
is => 'rwp'
Specifying "is => 'rwp'" will cause the following options to be set:
is => 'ro'
writer => "_set_$name"
is => 'lazy'
Specifying "is => 'lazy'" will cause the following options to be set:
is => 'ro'
builder => "_build_$name"
lazy => 1
NOTE: Since 0.009 we no longer set "init_arg => undef" if no "init_arg" is explicitly provided. This is
a change made in parallel with Moo, based on a large number of people surprised that lazy also made one's
"init_def" undefined.
is => 'lazy', default => ...
Specifying "is => 'lazy'" and a default will cause the following options to be set:
is => 'ro'
lazy => 1
default => ... # as provided
That is, if you specify "is => 'lazy'" and also provide a "default", then we won't try to set a builder,
as well.
builder => 1
Specifying "builder => 1" will cause the following options to be set:
builder => "_build_$name"
clearer => 1
Specifying "clearer => 1" will cause the following options to be set:
clearer => "clear_$name"
or, if your attribute name begins with an underscore:
clearer => "_clear$name"
(that is, an attribute named "_foo" would get "_clear_foo")
predicate => 1
Specifying "predicate => 1" will cause the following options to be set:
predicate => "has_$name"
or, if your attribute name begins with an underscore:
predicate => "_has$name"
(that is, an attribute named "_foo" would get "_has_foo")
trigger => 1
Specifying "trigger => 1" will cause the attribute to be created with a trigger that calls a named method
in the class with the options passed to the trigger. By default, the method name the trigger calls is
the name of the attribute prefixed with "_trigger_".
e.g., for an attribute named "foo" this would be equivalent to:
trigger => sub { shift->_trigger_foo(@_) }
For an attribute named "_foo":
trigger => sub { shift->_trigger__foo(@_) }
This naming scheme, in which the trigger is always private, is the same as the builder naming scheme
(just with a different prefix).
builder => sub { ... }
Passing a coderef to builder will cause that coderef to be installed in the class this attribute is
associated with the name you'd expect, and "builder => 1" to be set.
e.g., in your class,
has foo => (is => 'ro', builder => sub { 'bar!' });
...is effectively the same as...
has foo => (is => 'ro', builder => '_build_foo');
sub _build_foo { 'bar!' }
isa => ..., constraint => sub { ... }
Specifying the constraint option with a coderef will cause a new subtype constraint to be created, with
the parent type being the type specified in the "isa" option and the constraint being the coderef
supplied here.
For example, only integers greater than 10 will pass this attribute's type constraint:
# value must be an integer greater than 10 to pass the constraint
has thinger => (
isa => 'Int',
constraint => sub { $_ > 10 },
# ...
);
Note that if you supply a constraint, you must also provide an "isa".
isa => ..., constraint => sub { ... }, coerce => 1
Supplying a constraint and asking for coercion will "Just Work", that is, any coercions that the "isa"
type has will still work.
For example, let's say that you're using the "File" type constraint from MooseX::Types::Path::Class, and
you want an additional constraint that the file must exist:
has thinger => (
is => 'ro',
isa => File,
constraint => sub { !! $_->stat },
coerce => 1,
);
"thinger" will correctly coerce the string "/etc/passwd" to a "Path::Class:File", and will only accept
the coerced result as a value if the file exists.
coerce => [ Type => sub { ...coerce... }, ... ]
Specifying the coerce option with a hashref will cause a new subtype to be created and used (just as with
the constraint option, above), with the specified coercions added to the list. In the passed hashref,
the keys are Moose types (well, strings resolvable to Moose types), and the values are coderefs that will
coerce a given type to our type.
has bar => (
is => 'ro',
isa => 'Str',
coerce => [
Int => sub { "$_" },
Object => sub { 'An instance of ' . ref $_ },
],
);
ANONYMOUS SUBTYPING AND COERCION
Note that we create new, anonymous subtypes whenever the constraint or coercion options are specified in
such a way that the Shortcuts trait (this one) is invoked. It's fully supported to use both constraint
and coerce options at the same time.
This facility is intended to assist with the creation of one-off type constraints and coercions. It is
not possible to deliberately reuse the subtypes we create, and if you find yourself using a particular
isa / constraint / coerce option triplet in more than one place you should really think about creating a
type that you can reuse. MooseX::Types provides the facilities to easily do this, or even a simple
constant definition at the package level with an anonymous type stashed away for local use.
SEE ALSO
Please see those modules/websites for more information related to this module.
• MooseX::Types
SOURCE
The development version is on github at <http://github.com/RsrchBoy/moosex-attributeshortcuts> and may be cloned from <git://github.com/RsrchBoy/moosex-attributeshortcuts.git>
BUGS
Please report any bugs or feature requests on the bugtracker website
https://github.com/RsrchBoy/moosex-attributeshortcuts/issues
When submitting a bug or request, please include a test-file or a patch to an existing test-file that
illustrates the bug or desired feature.
AUTHOR
Chris Weyl <cweyl@alumni.drew.edu>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2011 by Chris Weyl.
This is free software, licensed under:
The GNU Lesser General Public License, Version 2.1, February 1999