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Type::Utils(3pm) User Contributed Perl Documentation Type::Utils(3pm)
NAME
Type::Utils - utility functions to make defining and using type constraints a little
easier
SYNOPSIS
package Types::Mine;
use Type::Library -base;
use Type::Utils -all;
BEGIN { extends "Types::Standard" };
declare "AllCaps",
as "Str",
where { uc($_) eq $_ },
inline_as { my $varname = $_[1]; "uc($varname) eq $varname" };
coerce "AllCaps",
from "Str", via { uc($_) };
STATUS
This module is covered by the Type-Tiny stability policy.
DESCRIPTION
This module provides utility functions to make defining and using type constraints a
little easier.
Type declaration functions
Many of the following are similar to the similarly named functions described in
Moose::Util::TypeConstraints.
"declare $name, %options"
"declare %options"
Declare a named or anonymous type constraint. Use "as" and "where" to specify the
parent type (if any) and (possibly) refine its definition.
declare EvenInt, as Int, where { $_ % 2 == 0 };
my $EvenInt = declare as Int, where { $_ % 2 == 0 };
NOTE: If the caller package inherits from Type::Library then any non-anonymous types
declared in the package will be automatically installed into the library.
Hidden gem: if you're inheriting from a type constraint that includes some coercions,
you can include "coercion => 1" in the %options hash to inherit the coercions.
"subtype $name, %options"
"subtype %options"
Declare a named or anonymous type constraint which is descended from an existing type
constraint. Use "as" and "where" to specify the parent type and refine its definition.
Actually, you should use "declare" instead; this is just an alias.
This function is not exported by default.
"type $name, %options"
"type %options"
Declare a named or anonymous type constraint which is not descended from an existing
type constraint. Use "where" to provide a coderef that constrains values.
Actually, you should use "declare" instead; this is just an alias.
This function is not exported by default.
"as $parent"
Used with "declare" to specify a parent type constraint:
declare EvenInt, as Int, where { $_ % 2 == 0 };
"where { BLOCK }"
Used with "declare" to provide the constraint coderef:
declare EvenInt, as Int, where { $_ % 2 == 0 };
The coderef operates on $_, which is the value being tested.
"message { BLOCK }"
Generate a custom error message when a value fails validation.
declare EvenInt,
as Int,
where { $_ % 2 == 0 },
message {
Int->validate($_) or "$_ is not divisible by two";
};
Without a custom message, the messages generated by Type::Tiny are along the lines of
Value "33" did not pass type constraint "EvenInt", which is usually reasonable.
"inline_as { BLOCK }"
Generate a string of Perl code that can be used to inline the type check into other
functions. If your type check is being used within a Moose or Moo constructor or
accessor methods, or used by Type::Params, this can lead to significant performance
improvements.
declare EvenInt,
as Int,
where { $_ % 2 == 0 },
inline_as {
my ($constraint, $varname) = @_;
my $perlcode =
$constraint->parent->inline_check($varname)
. "&& ($varname % 2 == 0)";
return $perlcode;
};
warn EvenInt->inline_check('$xxx'); # demonstration
Your "inline_as" block can return a list, in which case these will be smushed together
with "&&". The first item on the list may be undef, in which case the undef will be
replaced by the inlined parent type constraint. (And will throw an exception if there
is no parent.)
declare EvenInt,
as Int,
where { $_ % 2 == 0 },
inline_as {
return (undef, "($_ % 2 == 0)");
};
"class_type $name, { class => $package, %options }"
"class_type { class => $package, %options }"
"class_type $name"
Shortcut for declaring a Type::Tiny::Class type constraint.
If $package is omitted, is assumed to be the same as $name. If $name contains "::"
(which would be an invalid name as far as Type::Tiny is concerned), this will be
removed.
So for example, "class_type("Foo::Bar")" declares a Type::Tiny::Class type constraint
named "FooBar" which constrains values to objects blessed into the "Foo::Bar" package.
"role_type $name, { role => $package, %options }"
"role_type { role => $package, %options }"
"role_type $name"
Shortcut for declaring a Type::Tiny::Role type constraint.
If $package is omitted, is assumed to be the same as $name. If $name contains "::"
(which would be an invalid name as far as Type::Tiny is concerned), this will be
removed.
"duck_type $name, \@methods"
"duck_type \@methods"
Shortcut for declaring a Type::Tiny::Duck type constraint.
"union $name, \@constraints"
"union \@constraints"
Shortcut for declaring a Type::Tiny::Union type constraint.
"enum $name, \@values"
"enum \@values"
Shortcut for declaring a Type::Tiny::Enum type constraint.
"intersection $name, \@constraints"
"intersection \@constraints"
Shortcut for declaring a Type::Tiny::Intersection type constraint.
Coercion declaration functions
Many of the following are similar to the similarly named functions described in
Moose::Util::TypeConstraints.
"coerce $target, @coercions"
Add coercions to the target type constraint. The list of coercions is a list of type
constraint, conversion code pairs. Conversion code can be either a string of Perl code
or a coderef; in either case the value to be converted is $_.
"from $source"
Sugar to specify a type constraint in a list of coercions:
coerce EvenInt, from Int, via { $_ * 2 }; # As a coderef...
coerce EvenInt, from Int, q { $_ * 2 }; # or as a string!
"via { BLOCK }"
Sugar to specify a coderef in a list of coercions.
"declare_coercion $name, \%opts, $type1, $code1, ..."
"declare_coercion \%opts, $type1, $code1, ..."
Declares a coercion that is not explicitly attached to any type in the library. For
example:
declare_coercion "ArrayRefFromAny", from "Any", via { [$_] };
This coercion will be exportable from the library as a Type::Coercion object, but the
ArrayRef type exported by the library won't automatically use it.
Coercions declared this way are immutable (frozen).
"to_type $type"
Used with "declare_coercion" to declare the target type constraint for a coercion, but
still without explicitly attaching the coercion to the type constraint:
declare_coercion "ArrayRefFromAny",
to_type "ArrayRef",
from "Any", via { [$_] };
You should pretty much always use this when declaring an unattached coercion because
it's exceedingly useful for a type coercion to know what it will coerce to - this
allows it to skip coercion when no coercion is needed (e.g. avoiding coercing "[]" to
"[ [] ]") and allows "assert_coerce" to work properly.
Type library management
"extends @libraries"
Indicates that this type library extends other type libraries, importing their type
constraints.
Should usually be executed in a "BEGIN" block.
This is not exported by default because it's not fun to export it to Moo, Moose or
Mouse classes! "use Type::Utils -all" can be used to import it into your type library.
Other
"match_on_type $value => ($type => \&action, ..., \&default?)"
Something like a "switch"/"case" or "given"/"when" construct. Dispatches along
different code paths depending on the type of the incoming value. Example blatantly
stolen from the Moose documentation:
sub to_json
{
my $value = shift;
return match_on_type $value => (
HashRef() => sub {
my $hash = shift;
'{ '
. (
join ", " =>
map { '"' . $_ . '" : ' . to_json( $hash->{$_} ) }
sort keys %$hash
) . ' }';
},
ArrayRef() => sub {
my $array = shift;
'[ '.( join ", " => map { to_json($_) } @$array ).' ]';
},
Num() => q {$_},
Str() => q { '"' . $_ . '"' },
Undef() => q {'null'},
=> sub { die "$_ is not acceptable json type" },
);
}
Note that unlike Moose, code can be specified as a string instead of a coderef. (e.g.
for "Num", "Str" and "Undef" above.)
For improved performance, try "compile_match_on_type".
This function is not exported by default.
"my $coderef = compile_match_on_type($type => \&action, ..., \&default?)"
Compile a "match_on_type" block into a coderef. The following JSON converter is about
two orders of magnitude faster than the previous example:
sub to_json;
*to_json = compile_match_on_type(
HashRef() => sub {
my $hash = shift;
'{ '
. (
join ", " =>
map { '"' . $_ . '" : ' . to_json( $hash->{$_} ) }
sort keys %$hash
) . ' }';
},
ArrayRef() => sub {
my $array = shift;
'[ '.( join ", " => map { to_json($_) } @$array ).' ]';
},
Num() => q {$_},
Str() => q { '"' . $_ . '"' },
Undef() => q {'null'},
=> sub { die "$_ is not acceptable json type" },
);
Remember to store the coderef somewhere fairly permanent so that you don't compile it
over and over. "state" variables (in Perl >= 5.10) are good for this. (Same sort of
idea as Type::Params.)
This function is not exported by default.
"my $coderef = classifier(@types)"
Returns a coderef that can be used to classify values according to their type
constraint. The coderef, when passed a value, returns a type constraint which the
value satisfies.
use feature qw( say );
use Type::Utils qw( classifier );
use Types::Standard qw( Int Num Str Any );
my $classifier = classifier(Str, Int, Num, Any);
say $classifier->( "42" )->name; # Int
say $classifier->( "4.2" )->name; # Num
say $classifier->( [] )->name; # Any
Note that, for example, "42" satisfies Int, but it would satisfy the type constraints
Num, Str, and Any as well. In this case, the classifier has picked the most specific
type constraint that "42" satisfies.
If no type constraint is satisfied by the value, then the classifier will return
undef.
"dwim_type($string, %options)"
Given a string like "ArrayRef[Int|CodeRef]", turns it into a type constraint object,
hopefully doing what you mean.
It uses the syntax of Type::Parser. Firstly the Type::Registry for the caller package
is consulted; if that doesn't have a match, Types::Standard is consulted for standard
type constraint names.
If none of the above yields a type constraint, and the caller class is a Moose-based
class, then "dwim_type" attempts to look the type constraint up in the Moose type
registry. If it's a Mouse-based class, then the Mouse type registry is used instead.
If no type constraint can be found via these normal methods, several fallbacks are
available:
"lookup_via_moose"
Lookup in Moose registry even if caller is non-Moose class.
"lookup_via_mouse"
Lookup in Mouse registry even if caller is non-Mouse class.
"make_class_type"
Create a new Type::Tiny::Class constraint.
"make_role_type"
Create a new Type::Tiny::Role constraint.
You can alter which should be attempted, and in which order, by passing an option to
"dwim_type":
my $type = Type::Utils::dwim_type(
"ArrayRef[Int]",
fallback => [ "lookup_via_mouse" , "make_role_type" ],
);
For historical reasons, by default the fallbacks attempted are:
lookup_via_moose, lookup_via_mouse, make_class_type
You may set "fallback" to an empty arrayref to avoid using any of these fallbacks.
You can specify an alternative for the caller using the "for" option.
my $type = dwim_type("ArrayRef", for => "Moose::Object");
While it's probably better overall to use the proper Type::Registry interface for
resolving type constraint strings, this function often does what you want.
It should never die if it fails to find a type constraint (but may die if the type
constraint string is syntactically malformed), preferring to return undef.
This function is not exported by default.
"english_list(\$conjunction, @items)"
Joins the items with commas, placing a conjunction before the final item. The
conjunction is optional, defaulting to "and".
english_list(qw/foo bar baz/); # "foo, bar, and baz"
english_list(\"or", qw/quux quuux/); # "quux or quuux"
This function is not exported by default.
EXPORT
By default, all of the functions documented above are exported, except "subtype" and
"type" (prefer "declare" instead), "extends", "dwim_type",
"match_on_type"/"compile_match_on_type", "classifier", and "english_list".
This module uses Exporter::Tiny; see the documentation of that module for tips and tricks
importing from Type::Utils.
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, Types::Standard, Type::Coercion.
Type::Tiny::Class, Type::Tiny::Role, Type::Tiny::Duck, Type::Tiny::Enum,
Type::Tiny::Union.
Moose::Util::TypeConstraints, Mouse::Util::TypeConstraints.
AUTHOR
Toby Inkster <tobyink AT cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2013-2014, 2017-2019 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.
perl v5.30.0 2019-12-28 Type::Utils(3pm)
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On Apache
Under GNU General Public License
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