Toby Inkster > Type-Tiny > Type::Coercion

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Module Version: 0.038   Source   Latest Release: Type-Tiny-0.043_02

NAME ^

Type::Coercion - a set of coercions to a particular target type constraint

STATUS ^

This module is covered by the Type-Tiny stability policy.

DESCRIPTION ^

Constructors

new(%attributes)

Moose-style constructor function.

add($c1, $c2)

Create a Type::Coercion from two existing Type::Coercion objects.

Attributes

name

A name for the coercion. These need to conform to certain naming rules (they must begin with an uppercase letter and continue using only letters, digits 0-9 and underscores).

Optional; if not supplied will be an anonymous coercion.

display_name

A name to display for the coercion when stringified. These don't have to conform to any naming rules. Optional; a default name will be calculated from the name.

library

The package name of the type library this coercion is associated with. Optional. Informational only: setting this attribute does not install the coercion into the package.

type_constraint

Weak reference to the target type constraint (i.e. the type constraint which the output of coercion coderefs is expected to conform to).

type_coercion_map

Arrayref of source-type/code pairs. Don't set this in the constructor; use the add_type_coercions method instead.

compiled_coercion

Coderef to coerce a value ($_[0]).

The general point of this attribute is that you should not set it, and rely on the lazily-built default. Type::Coerce will usually generate a pretty fast coderef, inlining all type constraint checks, etc.

moose_coercion

A Moose::Meta::TypeCoercion object equivalent to this one. Don't set this manually; rely on the default built one.

frozen

Boolean; default false. A frozen coercion cannot have add_type_coercions called upon it.

Methods

has_type_constraint, has_library

Predicate methods.

is_anon

Returns true iff the coercion does not have a name.

qualified_name

For non-anonymous coercions that have a library, returns a qualified "Library::Type" sort of name. Otherwise, returns the same as name.

add_type_coercions($type1, $code1, ...)

Takes one or more pairs of Type::Tiny constraints and coercion code, creating an ordered list of source types and coercion codes.

Coercion codes can be expressed as either a string of Perl code (this includes objects which overload stringification), or a coderef (or object that overloads coderefification). In either case, the value to be coerced is $_.

coerce($value)

Coerce the value to the target type.

Returns the coerced value, or the original value if no coercion was possible.

assert_coerce($value)

Coerce the value to the target type, and throw an exception if the result does not validate against the target type constraint.

Returns the coerced value.

has_coercion_for_type($source_type)

Returns true iff this coercion has a coercion from the source type.

Returns the special string "0 but true" if no coercion should actually be necessary for this type. (For example, if a coercion coerces to a theoretical "Number" type, there is probably no coercion necessary for values that already conform to the "Integer" type.)

has_coercion_for_value($value)

Returns true iff the value could be coerced by this coercion.

Returns the special string "0 but true" if no coercion would be actually be necessary for this value (due to it already meeting the target type constraint).

can_be_inlined

Returns true iff the coercion can be inlined.

inline_coercion($varname)

Much like inline_coerce from Type::Tiny.

freeze

Set frozen to true. There is no unfreeze. Called automatically by Type::Tiny sometimes.

isa($class), can($method), AUTOLOAD(@args)

If Moose is loaded, then the combination of these methods is used to mock a Moose::Meta::TypeCoercion.

The following methods are used for parameterized coercions, but are not fully documented because they may change in the near future:

coercion_generator
has_coercion_generator
has_parameters
is_parameterizable
is_parameterized
parameterize(@params)
parameters

The following methods exist for Moose/Mouse compatibility, but do not do anything useful.

compile_type_coercion
meta

Overloading

DIAGNOSTICS ^

Attempt to add coercion code to a Type::Coercion which has been frozen

Type::Tiny type constraints are designed as immutable objects. Once you've created a constraint, rather than modifying it you generally create child constraints to do what you need.

Type::Coercion objects, on the other hand, are mutable. Coercion routines can be added at any time during the object's lifetime.

Sometimes Type::Tiny needs to freeze a Type::Coercion object to prevent this. In Moose and Mouse code this is likely to happen as soon as you use a type constraint in an attribute.

Workarounds:

  • Define as many of your coercions as possible within type libraries, not within the code that uses the type libraries. The type library will be evaluated relatively early, likely before there is any reason to freeze a coercion.
  • If you do need to add coercions to a type within application code outside the type library, instead create a subtype and add coercions to that. The plus_coercions method provided by Type::Tiny should make this simple.

BUGS ^

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Type-Tiny.

SEE ALSO ^

Type::Tiny::Manual.

Type::Tiny, Type::Library, Type::Utils, Types::Standard.

Type::Coercion::Union.

Moose::Meta::TypeCoercion.

AUTHOR ^

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE ^

This software is copyright (c) 2013-2014 by Toby Inkster.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

DISCLAIMER OF WARRANTIES ^

THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

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