2026-05-21 22:10 @216.73.216.105 CrawledBy Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
NAME
Type::Params - Params::Validate-like parameter validation using
Type::Tiny type constraints and coercions
SYNOPSIS
use v5.12;
use strict;
use warnings;
package Horse {
use Moo;
use Types::Standard qw( Object );
use Type::Params qw( compile );
use namespace::autoclean;
...; # define attributes, etc
sub add_child {
state $check = compile( Object, Object ); # method signature
my ($self, $child) = $check->(@_); # unpack @_
push @{ $self->children }, $child;
return $self;
}
}
package main;
my $boldruler = Horse->new;
$boldruler->add_child( Horse->new );
$boldruler->add_child( 123 ); # dies (123 is not an Object!)
STATUS
This module is covered by the Type-Tiny stability policy.
DESCRIPTION
This documents the details of the Type::Params package.
Type::Tiny::Manual is a better starting place if you're new.
Type::Params uses Type::Tiny constraints to validate the parameters to a
sub. It takes the slightly unorthodox approach of separating validation
into two stages:
1. Compiling the parameter specification into a coderef; then
2. Using the coderef to validate parameters.
The first stage is slow (it might take a couple of milliseconds), but
you only need to do it the first time the sub is called. The second
stage is fast; according to my benchmarks faster even than the XS
version of Params::Validate.
If you're using a modern version of Perl, you can use the "state"
keyword which was a feature added to Perl in 5.10. If you're stuck on
Perl 5.8, the example from the SYNOPSIS could be rewritten as:
my $add_child_check;
sub add_child {
$add_child_check ||= compile( Object, Object );
my ($self, $child) = $add_child_check->(@_); # unpack @_
push @{ $self->children }, $child;
return $self;
}
Not quite as neat, but not awful either.
If you don't like the two step, there's a shortcut reducing it to one
step:
use Type::Params qw( validate );
sub add_child {
my ($self, $child) = validate(\@_, Object, Object);
push @{ $self->children }, $child;
return $self;
}
Type::Params has a few tricks up its sleeve to make sure performance
doesn't suffer too much with the shortcut, but it's never going to be as
fast as the two stage compile/execute.
Functions
"compile(@spec)"
Given specifications for positional parameters, compiles a coderef that
can check against them.
The generalized form of specifications for positional parameters is:
state $check = compile(
\%general_opts,
$type_for_arg_1, \%opts_for_arg_1,
$type_for_arg_2, \%opts_for_arg_2,
$type_for_arg_3, \%opts_for_arg_3,
...,
slurpy($slurpy_type),
);
If a hashref of options is empty, it can simply be omitted. Much of the
time, you won't need to specify any options.
# In this example, we omit all the hashrefs
#
my $check = compile(
Str,
Int,
Optional[ArrayRef],
);
my ($str, $int, $arr) = $check->("Hello", 42, []); # ok
my ($str, $int, $arr) = $check->("", -1); # ok
my ($str, $int, $arr) = $check->("", -1, "bleh"); # dies
The coderef returned (i.e. $check) will check the arguments passed to it
conform to the spec (coercing them if appropriate), and return them as a
list if they do. If they don't, it will throw an exception.
The first hashref, before any type constraints, is for general options
which affect the entire compiled coderef. Currently supported general
options are:
"head" Int|ArrayRef[TypeTiny]
Parameters to shift off @_ before doing the main type check. These
parameters may also be checked, and cannot be optional or slurpy.
They may not have defaults.
my $check = compile(
{ head => [ Int, Int ] },
Str,
Str,
);
# ... is basically the same as...
my $check = compile(
Int,
Int,
Str,
Str,
);
A number may be given if you do not care to check types:
my $check = compile(
{ head => 2 },
Str,
Str,
);
# ... is basically the same as...
my $check = compile(
Any,
Any,
Str,
Str,
);
This is mostly useless for "compile", but can be useful for
"compile_named" and "compile_named_oo".
"tail" Int|ArrayRef[TypeTiny]
Similar to "head", but pops parameters off the end of @_ instead.
This is actually useful for "compile" because it allows you to sneak
in some required parameters *after* a slurpy or optional parameter.
my $check = compile(
{ tail => [ CodeRef ] },
slurpy ArrayRef[Str],
);
my ($strings, $coderef) = $check->("foo", "bar", sub { ... });
"want_source" Bool
Instead of returning a coderef, return Perl source code string.
Handy for debugging.
"want_details" Bool
Instead of returning a coderef, return a hashref of stuff including
the coderef. This is mostly for people extending Type::Params and I
won't go into too many details about what else this hashref
contains.
"description" Str
Description of the coderef that will show up in stack traces.
Defaults to "parameter validation for X" where X is the caller sub
name.
"subname" Str
If you wish to use the default description, but need to change the
sub name, use this.
"caller_level" Int
If you wish to use the default description, but need to change the
caller level for detecting the sub name, use this.
The types for each parameter may be any Type::Tiny type constraint, or
anything that Type::Tiny knows how to coerce into a Type::Tiny type
constraint, such as a MooseX::Types type constraint or a coderef.
Type coercions are automatically applied for all types that have
coercions.
If you wish to avoid coercions for a type, use Type::Tiny's
"no_coercions" method.
my $check = compile(
Int,
ArrayRef->of(Bool)->no_coercions,
);
Note that having any coercions in a specification, even if they're not
used in a particular check, will slightly slow down $check because it
means that $check can't just check @_ and return it unaltered if it's
valid — it needs to build a new array to return.
Optional parameters can be given using the Optional[] type constraint.
In the example above, the third parameter is optional. If it's present,
it's required to be an arrayref, but if it's absent, it is ignored.
Optional parameters need to be *after* required parameters in the spec.
An alternative way to specify optional parameters is using a parameter
options hashref.
my $check = compile(
Str,
Int,
ArrayRef, { optional => 1 },
);
The following parameter options are supported:
"optional" Bool
This is an alternative way of indicating that a parameter is
optional.
state $check = compile(
Int,
Int, { optional => 1 },
Optional[Int],
);
The two are not *exactly* equivalent. The exceptions thrown will
differ in the type name they mention. (Int versus Optional[Int].)
"default" CodeRef|Ref|Str|Undef
A default may be provided for a parameter.
state $check = compile(
Int,
Int, { default => "666" },
Int, { default => "999" },
);
Supported defaults are any strings (including numerical ones),
"undef", and empty hashrefs and arrayrefs. Non-empty hashrefs and
arrayrefs are *not allowed as defaults*.
Alternatively, you may provide a coderef to generate a default
value:
state $check = compile(
Int,
Int, { default => sub { 6 * 111 } },
Int, { default => sub { 9 * 111 } },
);
That coderef may generate any value, including non-empty arrayrefs
and non-empty hashrefs. For undef, simple strings, numbers, and
empty structures, avoiding using a coderef will make your parameter
processing faster.
The default *will* be validated against the type constraint, and
potentially coerced.
Note that having any defaults in a specification, even if they're
not used in a particular check, will slightly slow down $check
because it means that $check can't just check @_ and return it
unaltered if it's valid — it needs to build a new array to return.
As a special case, the numbers 0 and 1 may be used as shortcuts for
Optional[Any] and Any.
# Positional parameters
state $check = compile(1, 0, 0);
my ($foo, $bar, $baz) = $check->(@_); # $bar and $baz are optional
After any required and optional parameters may be a slurpy parameter.
Any additional arguments passed to $check will be slurped into an
arrayref or hashref and checked against the slurpy parameter. Defaults
are not supported for slurpy parameters.
Example with a slurpy ArrayRef:
sub xyz {
state $check = compile(Int, Int, slurpy ArrayRef[Int]);
my ($foo, $bar, $baz) = $check->(@_);
}
xyz(1..5); # $foo = 1
# $bar = 2
# $baz = [ 3, 4, 5 ]
Example with a slurpy HashRef:
my $check = compile(
Int,
Optional[Str],
slurpy HashRef[Int],
);
my ($x, $y, $z) = $check->(1, "y", foo => 666, bar => 999);
# $x is 1
# $y is "y"
# $z is { foo => 666, bar => 999 }
Any type constraints derived from ArrayRef or HashRef should work, but a
type does need to inherit from one of those because otherwise
Type::Params cannot know what kind of structure to slurp the remaining
arguments into.
slurpy Any is also allowed as a special case, and is treated as slurpy
ArrayRef.
From Type::Params 1.005000 onwards, slurpy hashrefs can be passed in as
a true hashref (which will be shallow cloned) rather than key-value
pairs.
sub xyz {
state $check = compile(Int, slurpy HashRef);
my ($num, $hr) = $check->(@_);
...
}
xyz( 5, foo => 1, bar => 2 ); # works
xyz( 5, { foo => 1, bar => 2 } ); # works from 1.005000
This feature is only implemented for slurpy hashrefs, not slurpy
arrayrefs.
Note that having a slurpy parameter will slightly slow down $check
because it means that $check can't just check @_ and return it unaltered
if it's valid — it needs to build a new array to return.
"validate(\@_, @spec)"
This example of "compile":
sub foo {
state $check = compile(@spec);
my @args = $check->(@_);
...;
}
Can be written using "validate" as:
sub foo {
my @args = validate(\@_, @spec);
...;
}
Performance using "compile" will *always* beat "validate" though.
"compile_named(@spec)"
"compile_named" is a variant of "compile" for named parameters instead
of positional parameters.
The format of the specification is changed to include names for each
parameter:
state $check = compile_named(
\%general_opts,
foo => $type_for_foo, \%opts_for_foo,
bar => $type_for_bar, \%opts_for_bar,
baz => $type_for_baz, \%opts_for_baz,
...,
extra => slurpy($slurpy_type),
);
The $check coderef will return a hashref.
my $check = compile_named(
foo => Int,
bar => Str, { default => "hello" },
);
my $args = $check->(foo => 42);
# $args->{foo} is 42
# $args->{bar} is "hello"
The %general_opts hash supports the same options as "compile" plus a few
additional options:
"class" ClassName
The check coderef will, instead of returning a simple hashref, call
"$class->new($hashref)" and return the result.
"constructor" Str
Specifies an alternative method name instead of "new" for the
"class" option described above.
"class" Tuple[ClassName, Str]
Shortcut for declaring both the "class" and "constructor" options at
once.
"bless" ClassName
Like "class", but bypass the constructor and directly bless the
hashref.
"named_to_list" Bool
Instead of returning a hashref, return a hash slice.
myfunc(bar => "x", foo => "y");
sub myfunc {
state $check = compile_named(
{ named_to_list => 1 },
foo => Str, { optional => 1 },
bar => Str, { optional => 1 },
);
my ($foo, $bar) = $check->(@_);
...; ## $foo is "y" and $bar is "x"
}
The order of keys for the hash slice is the same as the order of the
names passed to "compile_named". For missing named parameters,
"undef" is returned in the list.
Basically in the above example, "myfunc" takes named parameters, but
receieves positional parameters.
"named_to_list" ArrayRef[Str]
As above, but explicitly specify the keys of the hash slice.
Like "compile", the numbers 0 and 1 may be used as shortcuts for
Optional[Any] and Any.
state $check = compile_named(foo => 1, bar => 0, baz => 0);
my $args = $check->(@_); # $args->{bar} and $args->{baz} are optional
Slurpy parameters are slurped into a nested hashref.
my $check = compile(
foo => Str,
bar => Optional[Str],
extra => slurpy HashRef[Str],
);
my $args = $check->(foo => "aaa", quux => "bbb");
print $args->{foo}, "\n"; # aaa
print $args->{extra}{quux}, "\n"; # bbb
slurpy Any is treated as slurpy HashRef.
The "head" and "tail" options are supported. This allows for a mixture
of positional and named arguments, as long as the positional arguments
are non-optional and at the head and tail of @_.
my $check = compile(
{ head => [ Int, Int ], tail => [ CodeRef ] },
foo => Str,
bar => Str,
baz => Str,
);
my ($int1, $int2, $args, $coderef)
= $check->( 666, 999, foo=>'x', bar=>'y', baz=>'z', sub {...} );
say $args->{bar}; # 'y'
This can be combined with "named_to_list":
my $check = compile(
{ head => [ Int, Int ], tail => [ CodeRef ], named_to_list => 1 },
foo => Str,
bar => Str,
baz => Str,
);
my ($int1, $int2, $foo, $bar, $baz, $coderef)
= $check->( 666, 999, foo=>'x', bar=>'y', baz=>'z', sub {...} );
say $bar; # 'y'
"validate_named(\@_, @spec)"
Like "compile" has "validate", "compile_named" has "validate_named".
Just like "validate", it's the slower way to do things, so stick with
"compile_named".
"compile_named_oo(@spec)"
Here's a quick example function:
sub add_contact_to_database {
state $check = compile_named(
dbh => Object,
id => Int,
name => Str,
);
my $arg = $check->(@_);
my $sth = $arg->{db}->prepare('INSERT INTO contacts VALUES (?, ?)');
$sth->execute($arg->{id}, $arg->{name});
}
Looks simple, right? Did you spot that it will always die with an error
message *Can't call method "prepare" on an undefined value*?
This is because we defined a parameter called 'dbh' but later tried to
refer to it as $arg{db}. Here, Perl gives us a pretty clear error, but
sometimes the failures will be far more subtle. Wouldn't it be nice if
instead we could do this?
sub add_contact_to_database {
state $check = compile_named_oo(
dbh => Object,
id => Int,
name => Str,
);
my $arg = $check->(@_);
my $sth = $arg->dbh->prepare('INSERT INTO contacts VALUES (?, ?)');
$sth->execute($arg->id, $arg->name);
}
If we tried to call "$arg->db", it would fail because there was no such
method.
Well, that's exactly what "compile_named_oo" does.
As well as giving you nice protection against mistyped parameter names,
It also looks kinda pretty, I think. Hash lookups are a little faster
than method calls, of course (though Type::Params creates the methods
using Class::XSAccessor if it's installed, so they're still pretty
fast).
An optional parameter "foo" will also get a nifty "$arg->has_foo"
predicate method. Yay!
"compile_named_oo" gives you some extra options for parameters.
sub add_contact_to_database {
state $check = compile_named_oo(
dbh => Object,
id => Int, { default => '0', getter => 'identifier' },
name => Str, { optional => 1, predicate => 'has_name' },
);
my $arg = $check->(@_);
my $sth = $arg->dbh->prepare('INSERT INTO contacts VALUES (?, ?)');
$sth->execute($arg->identifier, $arg->name) if $arg->has_name;
}
"getter" Str
The "getter" option lets you choose the method name for getting the
argument value.
"predicate" Str
The "predicate" option lets you choose the method name for checking
the existence of an argument. By setting an explicit predicate
method name, you can force a predicate method to be generated for
non-optional arguments.
The objects returned by "compile_named_oo" are blessed into lightweight
classes which have been generated on the fly. Don't expect the names of
the classes to be stable or predictable. It's probably a bad idea to be
checking "can", "isa", or "DOES" on any of these objects. If you're
doing that, you've missed the point of them.
They don't have any constructor ("new" method). The $check coderef
effectively *is* the constructor.
"validate_named_oo(\@_, @spec)"
This function doesn't even exist. :D
"multisig(@alternatives)"
Type::Params can export a "multisig" function that compiles multiple
alternative signatures into one, and uses the first one that works:
state $check = multisig(
[ Int, ArrayRef ],
[ HashRef, Num ],
[ CodeRef ],
);
my ($int, $arrayref) = $check->( 1, [] ); # okay
my ($hashref, $num) = $check->( {}, 1.1 ); # okay
my ($code) = $check->( sub { 1 } ); # okay
$check->( sub { 1 }, 1.1 ); # throws an exception
Coercions, slurpy parameters, etc still work.
The magic global "${^TYPE_PARAMS_MULTISIG}" is set to the index of the
first signature which succeeded.
The present implementation involves compiling each signature
independently, and trying them each (in their given order!) in an "eval"
block. The only slightly intelligent part is that it checks if
"scalar(@_)" fits into the signature properly (taking into account
optional and slurpy parameters), and skips evals which couldn't possibly
succeed.
It's also possible to list coderefs as alternatives in "multisig":
state $check = multisig(
[ Int, ArrayRef ],
sub { ... },
[ HashRef, Num ],
[ CodeRef ],
compile_named( needle => Value, haystack => Ref ),
);
The coderef is expected to die if that alternative should be abandoned
(and the next alternative tried), or return the list of accepted
parameters. Here's a full example:
sub get_from {
state $check = multisig(
[ Int, ArrayRef ],
[ Str, HashRef ],
sub {
my ($meth, $obj);
die unless is_Object($obj);
die unless $obj->can($meth);
return ($meth, $obj);
},
);
my ($needle, $haystack) = $check->(@_);
for (${^TYPE_PARAMS_MULTISIG}) {
return $haystack->[$needle] if $_ == 0;
return $haystack->{$needle} if $_ == 1;
return $haystack->$needle if $_ == 2;
}
}
get_from(0, \@array); # returns $array[0]
get_from('foo', \%hash); # returns $hash{foo}
get_from('foo', $obj); # returns $obj->foo
The default error message is just "Parameter validation failed". You can
pass an option hashref as the first argument with an informative message
string:
sub foo {
state $OptionsDict = Dict[...];
state $check = multisig(
{ message => 'USAGE: $object->foo(\%options?, $string)' },
[ Object, $OptionsDict, StringLike ],
[ Object, StringLike ],
);
my ($self, @args) = $check->(@_);
my ($opts, $str) = ${^TYPE_PARAMS_MULTISIG} ? ({}, @args) : @_;
...;
}
$obj->foo(\%opts, "Hello");
$obj->foo("World");
"wrap_subs( $subname1, $wrapper1, ... )"
It's possible to turn the check inside-out and instead of the sub
calling the check, the check can call the original sub.
Normal way:
use Type::Param qw(compile);
use Types::Standard qw(Int Str);
sub foobar {
state $check = compile(Int, Str);
my ($foo, $bar) = @_;
...;
}
Inside-out way:
use Type::Param qw(wrap_subs);
use Types::Standard qw(Int Str);
sub foobar {
my ($foo, $bar) = @_;
...;
}
wrap_subs foobar => [Int, Str];
"wrap_subs" takes a hash of subs to wrap. The keys are the sub names and
the values are either arrayrefs of arguments to pass to "compile" to
make a check, or coderefs that have already been built by "compile",
"compile_named", or "compile_named_oo".
"wrap_methods( $subname1, $wrapper1, ... )"
"wrap_methods" also exists, which shifts off the invocant from @_ before
the check, but unshifts it before calling the original sub.
use Type::Param qw(wrap_subs);
use Types::Standard qw(Int Str);
sub foobar {
my ($self, $foo, $bar) = @_;
...;
}
wrap_subs foobar => [Int, Str];
Invocant
Type::Params exports a type Invocant on request. This gives you a type
constraint which accepts classnames *and* blessed objects.
use Type::Params qw( compile Invocant );
sub my_method {
state $check = compile(Invocant, ArrayRef, Int);
my ($self_or_class, $arr, $ix) = $check->(@_);
return $arr->[ $ix ];
}
ArgsObject
Type::Params exports a parameterizable type constraint ArgsObject. It
accepts the kinds of objects returned by "compile_named_oo" checks.
package Foo {
use Moo;
use Type::Params 'ArgsObject';
has args => (
is => 'ro',
isa => ArgsObject['Bar::bar'],
);
}
package Bar {
use Types::Standard -types;
use Type::Params 'compile_named_oo';
sub bar {
state $check = compile_named_oo(
xxx => Int,
yyy => ArrayRef,
);
my $args = &$check;
return 'Foo'->new( args => $args );
}
}
Bar::bar( xxx => 42, yyy => [] );
The parameter "Bar::bar" refers to the caller when the check is
compiled, rather than when the parameters are checked.
ENVIRONMENT
"PERL_TYPE_PARAMS_XS"
Affects the building of accessors for "compile_named_oo". If set to
true, will use Class::XSAccessor. If set to false, will use pure
Perl. If this environment variable does not exist, will use
Class::XSAccessor if it is available.
BUGS
Please report any bugs to
<https://github.com/tobyink/p5-type-tiny/issues>.
SEE ALSO
The Type::Tiny homepage <https://typetiny.toby.ink/>.
Type::Tiny, Type::Coercion, Types::Standard.
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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