# phpman > perldoc > Moose::Meta::TypeConstraint ## NAME [Moose::Meta::TypeConstraint](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeConstraint/markdown) - The Moose Type Constraint metaclass ## VERSION version 2.2200 ## DESCRIPTION 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](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeConstraint%3A%3ARegistry/markdown) object as objects of this class. ## INHERITANCE "[Moose::Meta::TypeConstraint](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeConstraint/markdown)" is a subclass of [Class::MOP::Object](https://www.chedong.com/phpMan.php/perldoc/Class%3A%3AMOP%3A%3AObject/markdown). ## METHODS [Moose::Meta::TypeConstraint](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeConstraint/markdown)->new(%options) 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](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeConstraint/markdown)" 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](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeCoercion/markdown) 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. $constraint->equals($type_name_or_object) Returns true if the supplied name or type object is the same as the current type. $constraint->is_subtype_of($type_name_or_object) Returns true if the supplied name or type object is a parent of the current type. $constraint->is_a_type_of($type_name_or_object) 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". $constraint->coerce($value) 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. $constraint->assert_coerce($value) This method behaves just like "coerce", but if the result is not valid according to $constraint, an error is thrown. $constraint->check($value) Returns true if the given value passes the constraint for the type. $constraint->validate($value) 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. $constraint->assert_valid($value) 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)". $constraint->name Returns the type's name, as provided to the constructor. $constraint->parent Returns the type's parent, as provided to the constructor, if any. $constraint->has_parent Returns true if the type has a parent type. $constraint->parents Returns all of the types parents as an list of type constraint objects. $constraint->constraint Returns the type's constraint, as provided to the constructor. $constraint->get_message($value) This generates a method for the given value. If the type does not have an explicit message, we generate a default message. $constraint->has_message Returns true if the type has a message. $constraint->message Returns the type's message as a subroutine reference. $constraint->coercion Returns the type's [Moose::Meta::TypeCoercion](https://www.chedong.com/phpMan.php/perldoc/Moose%3A%3AMeta%3A%3ATypeCoercion/markdown) object, if one exists. $constraint->has_coercion Returns true if the type has a coercion. $constraint->can_be_inlined 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. $constraint->create_child_type(%options) 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. ## BUGS See "BUGS" in Moose for details on reporting bugs. ## AUTHORS * Stevan Little <> * Dave Rolsky <> * Jesse Luehrs <> * Shawn M Moore <> * יובל קוג'מן (Yuval Kogman) <> * Karen Etheridge <> * Florian Ragwitz <> * Hans Dieter Pearcey <> * Chris Prather <> * Matt S Trout <> ## 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.