Moose Compatibility

Compatibility with Moose has been the utmost concern. The sugary interface is highly compatible with Moose. Even the error messages are taken from Moose. The Mouse code just runs its test suite 4x faster.

The idea is that, if you need the extra power, you should be able to run "s/Mouse/Moose/g" on your codebase and have nothing break. To that end, we have written Any::Moose which will act as Mouse unless Moose is loaded, in which case it will act as Moose. Since Mouse is a little sloppier than Moose, if you run into weird errors, it would be worth running:

    ANY_MOOSE=Moose perl your-script.pl

to see if the bug is caused by Mouse. Moose's diagnostics and validation are also better.

See also Mouse::Spec for compatibility and incompatibility with Moose.

Mouse Extentions

Please don't copy MooseX code to MouseX. If you need extensions, you really should upgrade to Moose. We don't need two parallel sets of extensions!

If you really must write a Mouse extension, please contact the Moose mailing list or #moose on IRC beforehand.

"$object->meta -> Mouse::Meta::Class"

Returns this class' metaclass instance.

"extends superclasses"

Sets this class' superclasses.

"before (method|methods|regexp) => CodeRef"

Installs a "before" method modifier. See "before" in Moose.

"after (method|methods|regexp) => CodeRef"

Installs an "after" method modifier. See "after" in Moose.

"around (method|methods|regexp) => CodeRef"

Installs an "around" method modifier. See "around" in Moose.

"has (name|names) => parameters"

Adds an attribute (or if passed an arrayref of names, multiple attributes) to this class. Options:

"is => ro|rw|bare"

The is option accepts either rw (for read/write), ro (for read only) or bare (for nothing). These will create either a read/write accessor or a read-only accessor respectively, using the same name as the $name of the attribute.

If you need more control over how your accessors are named, you can use the "reader", "writer" and "accessor" options, however if you use those, you won't need the is option.

"isa => TypeName | ClassName"

Provides type checking in the constructor and accessor. The following types are supported. Any unknown type is taken to be a class check (e.g. "isa => 'DateTime'" would accept only DateTime objects).

    Any Item Bool Undef Defined Value Num Int Str ClassName
    Ref ScalarRef ArrayRef HashRef CodeRef RegexpRef GlobRef
    FileHandle Object
    

For more documentation on type constraints, see Mouse::Util::TypeConstraints.

"does => RoleName"

This will accept the name of a role which the value stored in this attribute is expected to have consumed.

"coerce => Bool"

This will attempt to use coercion with the supplied type constraint to change the value passed into any accessors or constructors. You must have supplied a type constraint in order for this to work. See Moose::Cookbook::Basics::Recipe5 for an example.

"required => Bool"

Whether this attribute is required to have a value. If the attribute is lazy or has a builder, then providing a value for the attribute in the constructor is optional.

"init_arg => Str | Undef"

Allows you to use a different key name in the constructor. If undef, the attribute can't be passed to the constructor.

"default => Value | CodeRef"

Sets the default value of the attribute. If the default is a coderef, it will be invoked to get the default value. Due to quirks of Perl, any bare reference is forbidden, you must wrap the reference in a coderef. Otherwise, all instances will share the same reference.

"lazy => Bool"

If specified, the default is calculated on demand instead of in the constructor.

"predicate => Str"

Lets you specify a method name for installing a predicate method, which checks that the attribute has a value. It will not invoke a lazy default or builder method.

"clearer => Str"

Lets you specify a method name for installing a clearer method, which clears the attribute's value from the instance. On the next read, lazy or builder will be invoked.

"handles => HashRef|ArrayRef|Regexp"

Lets you specify methods to delegate to the attribute. ArrayRef forwards the given method names to method calls on the attribute. HashRef maps local method names to remote method names called on the attribute. Other forms of "handles", such as RoleName and CodeRef, are not yet supported.

"weak_ref => Bool"

Lets you automatically weaken any reference stored in the attribute.

Use of this feature requires Scalar::Util!

"trigger => CodeRef"

Any time the attribute's value is set (either through the accessor or the constructor), the trigger is called on it. The trigger receives as arguments the instance, and the new value.

"builder => Str"

Defines a method name to be called to provide the default value of the attribute. "builder => 'build_foo'" is mostly equivalent to "default => sub { $_[0]->build_foo }".

"auto_deref => Bool"

Allows you to automatically dereference ArrayRef and HashRef attributes in list context. In scalar context, the reference is returned (NOT the list length or bucket status). You must specify an appropriate type constraint to use auto_deref.

"lazy_build => Bool"

Automatically define the following options:

    has $attr => (
        # ...
        lazy      => 1
        builder   => "_build_$attr",
        clearer   => "clear_$attr",
        predicate => "has_$attr",
    );
    

"confess(message) -> BOOM"

"confess" in Carp for your convenience.

"blessed(value) -> ClassName | undef"

"blessed" in Scalar::Util for your convenience.

import

Importing Mouse will default your class' superclass list to Mouse::Object. You may use "extends" to replace the superclass list.

unimport

Please unimport Mouse ("no Mouse") so that if someone calls one of the keywords (such as "extends") it will break loudly instead breaking subtly.