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Karen Etheridge


Moose::Meta::TypeConstraint - The Moose Type Constraint metaclass


version 2.1210


This class represents a single type constraint. Moose's built-in type constraints, as well as constraints you define, are all stored in a Moose::Meta::TypeConstraint::Registry object as objects of this class.


Moose::Meta::TypeConstraint is a subclass of Class::MOP::Object.



This creates a new type constraint based on the provided %options:

  • name

    The constraint name. If a name is not provided, it will be set to "__ANON__".

  • parent

    A Moose::Meta::TypeConstraint object which is the parent type for the type being created. This is optional.

  • constraint

    This is the subroutine reference that implements the actual constraint check. This defaults to a subroutine which always returns true.

  • message

    A subroutine reference which is used to generate an error message when the constraint fails. This is optional.

  • coercion

    A Moose::Meta::TypeCoercion object representing the coercions to the type. This is optional.

  • inlined

    A subroutine which returns a string suitable for inlining this type constraint. It will be called as a method on the type constraint object, and will receive a single additional parameter, a variable name to be tested (usually "$_" or "$_[0]".

    This is optional.

  • inline_environment

    A hash reference of variables to close over. The keys are variables names, and the values are references to the variables.


Returns true if the supplied name or type object is the same as the current type.


Returns true if the supplied name or type object is a parent of the current type.


Returns true if the given type is the same as the current type, or is a parent of the current type. This is a shortcut for checking equals and is_subtype_of.


This will attempt to coerce the value to the type. If the type does not have any defined coercions this will throw an error.

If no coercion can produce a value matching $constraint, the original value is returned.


This method behaves just like coerce, but if the result is not valid according to $constraint, an error is thrown.


Returns true if the given value passes the constraint for the type.


This is similar to check. However, if the type is valid then the method returns an explicit undef. If the type is not valid, we call $self->get_message($value) internally to generate an error message.


Like check and validate, this method checks whether $value is valid under the constraint. If it is, it will return true. If it is not, an exception will be thrown with the results of $self->get_message($value).


Returns the type's name, as provided to the constructor.


Returns the type's parent, as provided to the constructor, if any.


Returns true if the type has a parent type.


Returns all of the types parents as an list of type constraint objects.


Returns the type's constraint, as provided to the constructor.


This generates a method for the given value. If the type does not have an explicit message, we generate a default message.


Returns true if the type has a message.


Returns the type's message as a subroutine reference.


Returns the type's Moose::Meta::TypeCoercion object, if one exists.


Returns true if the type has a coercion.


Returns true if this type constraint can be inlined. A type constraint which subtypes an inlinable constraint and does not add an additional constraint "inherits" its parent type's inlining.


This returns a new type constraint of the same class using the provided %options. The parent option will be the current type.

This method exists so that subclasses of this class can override this behavior and change how child types are created.


See "BUGS" in Moose for details on reporting bugs.


  • Stevan Little <stevan.little@iinteractive.com>

  • Dave Rolsky <autarch@urth.org>

  • Jesse Luehrs <doy@tozt.net>

  • Shawn M Moore <code@sartak.org>

  • יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>

  • Karen Etheridge <ether@cpan.org>

  • Florian Ragwitz <rafl@debian.org>

  • Hans Dieter Pearcey <hdp@weftsoar.net>

  • Chris Prather <chris@prather.org>

  • Matt S Trout <mst@shadowcat.co.uk>




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