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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 $type = dwim_type("ArrayRef", for => "Moose::Object");
While it's probably better overall to use the proper Type::Registry
interface for resolving type constraint strings, this function often
does what you want.
It should never die if it fails to find a type constraint (but may
die if the type constraint string is syntactically malformed),
preferring to return undef.
This function is not exported by default.
"is($type, $value)"
Shortcut for "$type->check($value)" but also if $type is a string,
will look it up via "dwim_type".
This function is not exported by default. This function is not even
exported by "use Type::Utils -all". You must request it explicitly.
use Type::Utils "is";
Beware using this in test scripts because it has the same name as a
function exported by Test::More. Note that you can rename this
function if "is" will cause conflicts:
use Type::Utils "is" => { -as => "isntnt" };
"assert($type, $value)"
Like "is" but instead of returning a boolean, returns $value and
dies if the value fails the type check.
This function is not exported by default, but it is exported by "use
Type::Utils -all".
"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
<https://github.com/tobyink/p5-type-tiny/issues>.
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, 2017-2021 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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