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Moose::Util::TypeConstraints(3pUser Contributed Perl DocumentatiMoose::Util::TypeConstraints(3pm)
NAME
Moose::Util::TypeConstraints - Type constraint system for Moose
VERSION
version 2.2200
SYNOPSIS
use Moose::Util::TypeConstraints;
subtype 'Natural',
as 'Int',
where { $_ > 0 };
subtype 'NaturalLessThanTen',
as 'Natural',
where { $_ < 10 },
message { "This number ($_) is not less than ten!" };
coerce 'Num',
from 'Str',
via { 0+$_ };
class_type 'DateTimeClass', { class => 'DateTime' };
role_type 'Barks', { role => 'Some::Library::Role::Barks' };
enum 'RGBColors', [qw(red green blue)];
union 'StringOrArray', [qw( String ArrayRef )];
no Moose::Util::TypeConstraints;
DESCRIPTION
This module provides Moose with the ability to create custom type constraints to be used
in attribute definition.
Important Caveat
This is NOT a type system for Perl 5. These are type constraints, and they are not used by
Moose unless you tell it to. No type inference is performed, expressions are not typed,
etc. etc. etc.
A type constraint is at heart a small "check if a value is valid" function. A constraint
can be associated with an attribute. This simplifies parameter validation, and makes your
code clearer to read, because you can refer to constraints by name.
Slightly Less Important Caveat
It is always a good idea to quote your type names.
This prevents Perl from trying to execute the call as an indirect object call. This can be
an issue when you have a subtype with the same name as a valid class.
For instance:
subtype DateTime => as Object => where { $_->isa('DateTime') };
will just work, while this:
use DateTime;
subtype DateTime => as Object => where { $_->isa('DateTime') };
will fail silently and cause many headaches. The simple way to solve this, as well as
future proof your subtypes from classes which have yet to have been created, is to quote
the type name:
use DateTime;
subtype 'DateTime', as 'Object', where { $_->isa('DateTime') };
Default Type Constraints
This module also provides a simple hierarchy for Perl 5 types, here is that hierarchy
represented visually.
Any
Item
Bool
Maybe[`a]
Undef
Defined
Value
Str
Num
Int
ClassName
RoleName
Ref
ScalarRef[`a]
ArrayRef[`a]
HashRef[`a]
CodeRef
RegexpRef
GlobRef
FileHandle
Object
NOTE: Any type followed by a type parameter "[`a]" can be parameterized, this means you
can say:
ArrayRef[Int] # an array of integers
HashRef[CodeRef] # a hash of str to CODE ref mappings
ScalarRef[Int] # a reference to an integer
Maybe[Str] # value may be a string, may be undefined
If Moose finds a name in brackets that it does not recognize as an existing type, it
assumes that this is a class name, for example "ArrayRef[DateTime]".
NOTE: Unless you parameterize a type, then it is invalid to include the square brackets.
I.e. "ArrayRef[]" will be treated as a new type name, not as a parameterization of
"ArrayRef".
NOTE: The "Undef" type constraint for the most part works correctly now, but edge cases
may still exist, please use it sparingly.
NOTE: The "ClassName" type constraint does a complex package existence check. This means
that your class must be loaded for this type constraint to pass.
NOTE: The "RoleName" constraint checks a string is a package name which is a role, like
'MyApp::Role::Comparable'.
Type Constraint Naming
Type names declared via this module can only contain alphanumeric characters, colons (:),
and periods (.).
Since the types created by this module are global, it is suggested that you namespace your
types just as you would namespace your modules. So instead of creating a Color type for
your My::Graphics module, you would call the type My::Graphics::Types::Color instead.
Use with Other Constraint Modules
This module can play nicely with other constraint modules with some slight tweaking. The
"where" clause in types is expected to be a "CODE" reference which checks its first
argument and returns a boolean. Since most constraint modules work in a similar way, it
should be simple to adapt them to work with Moose.
For instance, this is how you could use it with Declare::Constraints::Simple to declare a
completely new type.
type 'HashOfArrayOfObjects',
where {
IsHashRef(
-keys => HasLength,
-values => IsArrayRef(IsObject)
)->(@_);
};
For more examples see the t/examples/example_w_DCS.t test file.
Here is an example of using Test::Deep and its non-test related "eq_deeply" function.
type 'ArrayOfHashOfBarsAndRandomNumbers',
where {
eq_deeply($_,
array_each(subhashof({
bar => isa('Bar'),
random_number => ignore()
})))
};
For a complete example see the t/examples/example_w_TestDeep.t test file.
Error messages
Type constraints can also specify custom error messages, for when they fail to validate.
This is provided as just another coderef, which receives the invalid value in $_, as in:
subtype 'PositiveInt',
as 'Int',
where { $_ > 0 },
message { "$_ is not a positive integer!" };
If no message is specified, a default message will be used, which indicates which type
constraint was being used and what value failed. If Devel::PartialDump (version 0.14 or
higher) is installed, it will be used to display the invalid value, otherwise it will just
be printed as is.
FUNCTIONS
Type Constraint Constructors
The following functions are used to create type constraints. They will also register the
type constraints your create in a global registry that is used to look types up by name.
See the "SYNOPSIS" for an example of how to use these.
subtype 'Name', as 'Parent', where { } ...
This creates a named subtype.
If you provide a parent that Moose does not recognize, it will automatically create a new
class type constraint for this name.
When creating a named type, the "subtype" function should either be called with the sugar
helpers ("where", "message", etc), or with a name and a hashref of parameters:
subtype( 'Foo', { where => ..., message => ... } );
The valid hashref keys are "as" (the parent), "where", "message", and "inline_as".
subtype as 'Parent', where { } ...
This creates an unnamed subtype and will return the type constraint meta-object, which
will be an instance of Moose::Meta::TypeConstraint.
When creating an anonymous type, the "subtype" function should either be called with the
sugar helpers ("where", "message", etc), or with just a hashref of parameters:
subtype( { where => ..., message => ... } );
class_type ($class, ?$options)
Creates a new subtype of "Object" with the name $class and the metaclass
Moose::Meta::TypeConstraint::Class.
# Create a type called 'Box' which tests for objects which ->isa('Box')
class_type 'Box';
By default, the name of the type and the name of the class are the same, but you can
specify both separately.
# Create a type called 'Box' which tests for objects which ->isa('ObjectLibrary::Box');
class_type 'Box', { class => 'ObjectLibrary::Box' };
role_type ($role, ?$options)
Creates a "Role" type constraint with the name $role and the metaclass
Moose::Meta::TypeConstraint::Role.
# Create a type called 'Walks' which tests for objects which ->does('Walks')
role_type 'Walks';
By default, the name of the type and the name of the role are the same, but you can
specify both separately.
# Create a type called 'Walks' which tests for objects which ->does('MooseX::Role::Walks');
role_type 'Walks', { role => 'MooseX::Role::Walks' };
maybe_type ($type)
Creates a type constraint for either "undef" or something of the given type.
duck_type ($name, \@methods)
This will create a subtype of Object and test to make sure the value "can()" do the
methods in "\@methods".
This is intended as an easy way to accept non-Moose objects that provide a certain
interface. If you're using Moose classes, we recommend that you use a "requires"-only Role
instead.
duck_type (\@methods)
If passed an ARRAY reference as the only parameter instead of the $name, "\@methods" pair,
this will create an unnamed duck type. This can be used in an attribute definition like
so:
has 'cache' => (
is => 'ro',
isa => duck_type( [qw( get_set )] ),
);
enum ($name, \@values)
This will create a basic subtype for a given set of strings. The resulting constraint
will be a subtype of "Str" and will match any of the items in "\@values". It is case
sensitive. See the "SYNOPSIS" for a simple example.
NOTE: This is not a true proper enum type, it is simply a convenient constraint builder.
enum (\@values)
If passed an ARRAY reference as the only parameter instead of the $name, "\@values" pair,
this will create an unnamed enum. This can then be used in an attribute definition like
so:
has 'sort_order' => (
is => 'ro',
isa => enum([qw[ ascending descending ]]),
);
union ($name, \@constraints)
This will create a basic subtype where any of the provided constraints may match in order
to satisfy this constraint.
union (\@constraints)
If passed an ARRAY reference as the only parameter instead of the $name, "\@constraints"
pair, this will create an unnamed union. This can then be used in an attribute definition
like so:
has 'items' => (
is => 'ro',
isa => union([qw[ Str ArrayRef ]]),
);
This is similar to the existing string union:
isa => 'Str|ArrayRef'
except that it supports anonymous elements as child constraints:
has 'color' => (
isa => 'ro',
isa => union([ 'Int', enum([qw[ red green blue ]]) ]),
);
as 'Parent'
This is just sugar for the type constraint construction syntax.
It takes a single argument, which is the name of a parent type.
where { ... }
This is just sugar for the type constraint construction syntax.
It takes a subroutine reference as an argument. When the type constraint is tested, the
reference is run with the value to be tested in $_. This reference should return true or
false to indicate whether or not the constraint check passed.
message { ... }
This is just sugar for the type constraint construction syntax.
It takes a subroutine reference as an argument. When the type constraint fails, then the
code block is run with the value provided in $_. This reference should return a string,
which will be used in the text of the exception thrown.
inline_as { ... }
This can be used to define a "hand optimized" inlinable version of your type constraint.
You provide a subroutine which will be called as a method on a Moose::Meta::TypeConstraint
object. It will receive a single parameter, the name of the variable to check, typically
something like "$_" or "$_[0]".
The subroutine should return a code string suitable for inlining. You can assume that the
check will be wrapped in parentheses when it is inlined.
The inlined code should include any checks that your type's parent types do. If your
parent type constraint defines its own inlining, you can simply use that to avoid
repeating code. For example, here is the inlining code for the "Value" type, which is a
subtype of "Defined":
sub {
$_[0]->parent()->_inline_check($_[1])
. ' && !ref(' . $_[1] . ')'
}
type 'Name', where { } ...
This creates a base type, which has no parent.
The "type" function should either be called with the sugar helpers ("where", "message",
etc), or with a name and a hashref of parameters:
type( 'Foo', { where => ..., message => ... } );
The valid hashref keys are "where", "message", and "inlined_as".
Type Constraint Utilities
match_on_type $value => ( $type => \&action, ... ?\&default )
This is a utility function for doing simple type based dispatching similar to match/case
in OCaml and case/of in Haskell. It is not as featureful as those languages, nor does not
it support any kind of automatic destructuring bind. Here is a simple Perl pretty printer
dispatching over the core Moose types.
sub ppprint {
my $x = shift;
match_on_type $x => (
HashRef => sub {
my $hash = shift;
'{ '
. (
join ", " => map { $_ . ' => ' . ppprint( $hash->{$_} ) }
sort keys %$hash
) . ' }';
},
ArrayRef => sub {
my $array = shift;
'[ ' . ( join ", " => map { ppprint($_) } @$array ) . ' ]';
},
CodeRef => sub {'sub { ... }'},
RegexpRef => sub { 'qr/' . $_ . '/' },
GlobRef => sub { '*' . B::svref_2object($_)->NAME },
Object => sub { $_->can('to_string') ? $_->to_string : $_ },
ScalarRef => sub { '\\' . ppprint( ${$_} ) },
Num => sub {$_},
Str => sub { '"' . $_ . '"' },
Undef => sub {'undef'},
=> sub { die "I don't know what $_ is" }
);
}
Or a simple JSON serializer:
sub to_json {
my $x = shift;
match_on_type $x => (
HashRef => sub {
my $hash = shift;
'{ '
. (
join ", " =>
map { '"' . $_ . '" : ' . to_json( $hash->{$_} ) }
sort keys %$hash
) . ' }';
},
ArrayRef => sub {
my $array = shift;
'[ ' . ( join ", " => map { to_json($_) } @$array ) . ' ]';
},
Num => sub {$_},
Str => sub { '"' . $_ . '"' },
Undef => sub {'null'},
=> sub { die "$_ is not acceptable json type" }
);
}
The matcher is done by mapping a $type to an "\&action". The $type can be either a string
type or a Moose::Meta::TypeConstraint object, and "\&action" is a subroutine reference.
This function will dispatch on the first match for $value. It is possible to have a catch-
all by providing an additional subroutine reference as the final argument to
"match_on_type".
Type Coercion Constructors
You can define coercions for type constraints, which allow you to automatically transform
values to something valid for the type constraint. If you ask your accessor to coerce by
adding the option "coerce => 1", then Moose will run the type-coercion code first,
followed by the type constraint check. This feature should be used carefully as it is very
powerful and could easily take off a limb if you are not careful.
See the "SYNOPSIS" for an example of how to use these.
coerce 'Name', from 'OtherName', via { ... }
This defines a coercion from one type to another. The "Name" argument is the type you are
coercing to.
To define multiple coercions, supply more sets of from/via pairs:
coerce 'Name',
from 'OtherName', via { ... },
from 'ThirdName', via { ... };
from 'OtherName'
This is just sugar for the type coercion construction syntax.
It takes a single type name (or type object), which is the type being coerced from.
via { ... }
This is just sugar for the type coercion construction syntax.
It takes a subroutine reference. This reference will be called with the value to be
coerced in $_. It is expected to return a new value of the proper type for the coercion.
Creating and Finding Type Constraints
These are additional functions for creating and finding type constraints. Most of these
functions are not available for importing. The ones that are importable as specified.
find_type_constraint($type_name)
This function can be used to locate the Moose::Meta::TypeConstraint object for a named
type.
This function is importable.
register_type_constraint($type_object)
This function will register a Moose::Meta::TypeConstraint with the global type registry.
This function is importable.
normalize_type_constraint_name($type_constraint_name)
This method takes a type constraint name and returns the normalized form. This removes any
whitespace in the string.
create_type_constraint_union($pipe_separated_types | @type_constraint_names)
create_named_type_constraint_union($name, $pipe_separated_types | @type_constraint_names)
This can take a union type specification like 'Int|ArrayRef[Int]', or a list of names. It
returns a new Moose::Meta::TypeConstraint::Union object.
create_parameterized_type_constraint($type_name)
Given a $type_name in the form of 'BaseType[ContainerType]', this will create a new
Moose::Meta::TypeConstraint::Parameterized object. The "BaseType" must already exist as a
parameterizable type.
create_class_type_constraint($class, $options)
Given a class name this function will create a new Moose::Meta::TypeConstraint::Class
object for that class name.
The $options is a hash reference that will be passed to the
Moose::Meta::TypeConstraint::Class constructor (as a hash).
create_role_type_constraint($role, $options)
Given a role name this function will create a new Moose::Meta::TypeConstraint::Role object
for that role name.
The $options is a hash reference that will be passed to the
Moose::Meta::TypeConstraint::Role constructor (as a hash).
create_enum_type_constraint($name, $values)
Given a enum name this function will create a new Moose::Meta::TypeConstraint::Enum object
for that enum name.
create_duck_type_constraint($name, $methods)
Given a duck type name this function will create a new
Moose::Meta::TypeConstraint::DuckType object for that enum name.
find_or_parse_type_constraint($type_name)
Given a type name, this first attempts to find a matching constraint in the global
registry.
If the type name is a union or parameterized type, it will create a new object of the
appropriate, but if given a "regular" type that does not yet exist, it simply returns
false.
When given a union or parameterized type, the member or base type must already exist.
If it creates a new union or parameterized type, it will add it to the global registry.
find_or_create_isa_type_constraint($type_name)
find_or_create_does_type_constraint($type_name)
These functions will first call "find_or_parse_type_constraint". If that function does not
return a type, a new type object will be created.
The "isa" variant will use "create_class_type_constraint" and the "does" variant will use
"create_role_type_constraint".
get_type_constraint_registry
Returns the Moose::Meta::TypeConstraint::Registry object which keeps track of all type
constraints.
list_all_type_constraints
This will return a list of type constraint names in the global registry. You can then
fetch the actual type object using "find_type_constraint($type_name)".
list_all_builtin_type_constraints
This will return a list of builtin type constraints, meaning those which are defined in
this module. See the "Default Type Constraints" section for a complete list.
export_type_constraints_as_functions
This will export all the current type constraints as functions into the caller's namespace
("Int()", "Str()", etc). Right now, this is mostly used for testing, but it might prove
useful to others.
get_all_parameterizable_types
This returns all the parameterizable types that have been registered, as a list of type
objects.
add_parameterizable_type($type)
Adds $type to the list of parameterizable types
BUGS
See "BUGS" in Moose for details on reporting bugs.
AUTHORS
o Stevan Little <stevan AT cpan.org>
o Dave Rolsky <autarch AT urth.org>
o Jesse Luehrs <doy AT cpan.org>
o Shawn M Moore <sartak AT cpan.org>
o ' (Yuval Kogman) <nothingmuch AT woobling.org>
o Karen Etheridge <ether AT cpan.org>
o Florian Ragwitz <rafl AT debian.org>
o Hans Dieter Pearcey <hdp AT cpan.org>
o Chris Prather <chris AT prather.org>
o Matt S Trout <mstrout AT cpan.org>
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.
perl v5.34.0 2022-02-06 Moose::Util::TypeConstraints(3pm)
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On Apache
Under GNU General Public License
2024-12-12 19:40 @3.137.163.165 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)