NAME
Type::Params - sub signature validation using Type::Tiny type constraints and coercions
SYNOPSIS
use v5.36;
package Horse {
use Moo;
use Types::Standard qw( Object );
use Type::Params -sigs;
use namespace::autoclean;
...; # define attributes, etc
signature_for add_child => (
method => 1,
positional => [ Object ],
);
sub add_child ( $self, $child ) {
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:
Compiling the parameter specification into a coderef; then
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.
MODERN API
The modern API can be exported using:
use Type::Params -sigs;
Or:
use Type::Params -v2;
Or by requesting functions by name:
use Type::Params qw( signature signature_for );
signature( %spec )
The signature
function takes a specification for your function's signature and returns a coderef. You then call the coderef in list context, passing @_
to it. The coderef will check, coerce, and apply other procedures to the values, and return the tidied values, or die with an error.
The usual way of using it is:
sub your_function {
state $signature = signature( ... );
my ( $arg1, $arg2, $arg3 ) = $signature->( @_ );
...;
}
Perl allows a slightly archaic way of calling coderefs without using parentheses, which may be slightly faster at the cost of being more obscure:
sub your_function {
state $signature = signature( ... );
my ( $arg1, $arg2, $arg3 ) = &$signature;
...;
}
If you need to support Perl 5.8, which didn't have the state
keyword:
my $__your_function_sig;
sub your_function {
$__your_function_sig ||= signature( ... );
my ( $arg1, $arg2, $arg3 ) = $__your_function_sig->( @_ );
...;
}
One important thing to note is how the signature is only compiled into a coderef the first time your function gets called, and thereafter will be reused.
Signature Specification Options
The signature specification is a hash which must contain either a positional
, named
, or multiple
key indicating whether your function takes positional parameters, named parameters, or supports multiple calling conventions, but may also include other options.
positional
ArrayRef
This is conceptually a list of type constraints, one for each positional parameter. For example, a signature for a function which accepts two integers:
signature( positional => [ Int, Int ] )
However, each type constraint is optionally followed by a hashref of options which affect that parameter. For example:
signature( positional => [
Int, { default => 40 },
Int, { default => 2 },
] )
Type constraints can instead be given as strings, which will be looked up using dwim_type
from Type::Utils.
signature( positional => [
'Int', { default => 40 },
'Int', { default => 2 },
] )
See the section below for more information on parameter options.
Optional parameters must follow required parameters, and can be specified using either the Optional parameterizable type constraint, the optional
parameter option, or by providing a default.
signature( positional => [
Optional[Int],
Int, { optional => !!1 },
Int, { default => 42 },
] )
A single slurpy parameter may be provided at the end, using the Slurpy parameterizable type constraint, or the slurpy
parameter option:
signature( positional => [
Int,
Slurpy[ ArrayRef[Int] ],
] )
signature( positional => [
Int,
ArrayRef[Int], { slurpy => !!1 },
] )
The positional
option can also be abbreviated to pos
.
So signature( pos => [...] )
can be used instead of the longer signature( positional => [...] )
.
If a signature uses positional parameters, the values are returned by the coderef as a list:
sub add_numbers {
state $sig = signature( positional => [ Num, Num ] );
my ( $num1, $num2 ) = $sig->( @_ );
return $num1 + $num2;
}
say add_numbers( 2, 3 ); # says 5
named
ArrayRef
This is conceptually a list of pairs of names and type constraints, one name+type pair for each named parameter. For example, a signature for a function which accepts two integers:
signature( named => [ foo => Int, bar => Int ] )
However, each type constraint is optionally followed by a hashref of options which affect that parameter. For example:
signature( named => [
foo => Int, { default => 40 },
bar => Int, { default => 2 },
] )
Type constraints can instead be given as strings, which will be looked up using dwim_type
from Type::Utils.
signature( named => [
foo => 'Int', { default => 40 },
bar => 'Int', { default => 2 },
] )
Optional and slurpy parameters are allowed, but unlike positional parameters, they do not need to be at the end.
See the section below for more information on parameter options.
If a signature uses named parameters, the values are returned by the coderef as an object:
sub add_numbers {
state $sig = signature( named => [ num1 => Num, num2 => Num ] );
my ( $arg ) = $sig->( @_ );
return $arg->num1 + $arg->num2;
}
say add_numbers( num1 => 2, num2 => 3 ); # says 5
say add_numbers( { num1 => 2, num2 => 3 } ); # also says 5
named_to_list
ArrayRef|Bool
The named_to_list
option is ignored for signatures using positional parameters, but for signatures using named parameters, allows them to be returned in a list instead of as an object:
sub add_numbers {
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
named_to_list => !!1,
);
my ( $num1, $num2 ) = $sig->( @_ );
return $num1 + $num2;
}
say add_numbers( num1 => 2, num2 => 3 ); # says 5
say add_numbers( { num1 => 2, num2 => 3 } ); # also says 5
You can think of add_numbers
above as a function which takes named parameters from the outside, but receives positional parameters on the inside.
You can use an arrayref to specify the order the parameters will be returned in. (By default they are returned in the order they were defined in.)
sub add_numbers {
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
named_to_list => [ qw( num2 num1 ) ],
);
my ( $num2, $num1 ) = $sig->( @_ );
return $num1 + $num2;
}
head
Int|ArrayRef
head
provides an additional list of non-optional, positional parameters at the start of @_
. This is often used for method calls. For example, if you wish to define a signature for:
$object->my_method( foo => 123, bar => 456 );
You could write it as this:
sub my_method {
state $signature = signature(
head => [ Object ],
named => [ foo => Optional[Int], bar => Optional[Int] ],
);
my ( $self, $arg ) = $signature->( @_ );
...;
}
If head
is set as a number instead of an arrayref, it is the number of additional arguments at the start:
sub my_method {
state $signature = signature(
head => 1,
named => [ foo => Optional[Int], bar => Optional[Int] ],
);
my ( $self, $arg ) = $signature->( @_ );
...;
}
In this case, no type checking is performed on those additional arguments; it is just checked that they exist.
tail
Int|ArrayRef
A tail
is like a head
except that it is for arguments at the end of @_
.
sub my_method {
state $signature = signature(
head => [ Object ],
named => [ foo => Optional[Int], bar => Optional[Int] ],
tail => [ CodeRef ],
);
my ( $self, $arg, $callback ) = $signature->( @_ );
...;
}
$object->my_method( foo => 123, bar => 456, sub { ... } );
method
Bool|TypeTiny
While head
can be used for method signatures, a more declarative way is to set method => 1
.
If you wish to be specific that this is an object method, intended to be called on blessed objects only, then you may use method => Object
, using the Object type from Types::Standard. If you wish to specify that it's a class method, then use method => Str
, using the Str type from Types::Standard. (method => ClassName
is perhaps clearer, but it's a slower check.)
sub my_method {
state $signature = signature(
method => 1,
named => [ foo => Optional[Int], bar => Optional[Int] ],
);
my ( $self, $arg ) = $signature->( @_ );
...;
}
If method
is true (or a type constraint) then any parameter defaults which are coderefs will be called as methods.
description
Str
This is the description of the coderef that will show up in stack traces. It defaults to "parameter validation for X" where X is the caller sub name. Usually the default will be fine.
package
Str
The package of the sub whose parameters we're supposed to be checking. As well as showing up in stack traces, it's used by dwim_type
if you provide any type constraints as strings.
The default is probably fine, but if you're wrapping signature
so that you can check signatures on behalf of another package, you may need to provide it.
subname
Str
The name of the sub whose parameters we're supposed to be checking.
The default is probably fine, but if you're wrapping signature
so that you can check signatures on behalf of another package, you may need to provide it.
caller_level
Int
If you're wrapping signature
so that you can check signatures on behalf of another package, then setting caller_level
to 1 (or more, depending on the level of wrapping!) may be an alternative to manually setting the package
and subname
.
on_die
Maybe[CodeRef]
Usually when your coderef hits an error, it will throw an exception, which is a blessed Error::TypeTiny object.
If you provide an on_die
coderef, then instead the Error::TypeTiny object will be passed to it. If the on_die
coderef returns something, then whatever it returns will be returned as your signature's parameters.
sub add_numbers {
state $sig = signature(
positional => [ Num, Num ],
on_die => sub {
my $error = shift;
print "Existential crisis: $error\n";
exit( 1 );
},
);
my ( $num1, $num2 ) = $sig->( @_ );
return $num1 + $num2;
}
say add_numbers(); # has an existential crisis
This is probably not very useful.
goto_next
Bool|CodeLike
This can be used for chaining coderefs. If you understand on_die
, it's more like an "on_live".
sub add_numbers {
state $sig = signature(
positional => [ Num, Num ],
goto_next => sub {
my ( $num1, $num2 ) = @_;
return $num1 + $num2;
},
);
my $sum = $sig->( @_ );
return $sum;
}
say add_numbers( 2, 3 ); # says 5
If set to a true boolean instead of a coderef, has a slightly different behaviour:
sub add_numbers {
state $sig = signature(
positional => [ Num, Num ],
goto_next => !!1,
);
my $sum = $sig->(
sub { return $_[0] + $_[1] },
@_,
);
return $sum;
}
say add_numbers( 2, 3 ); # says 5
This looks strange. Why would this be useful? Well, it works nicely with Moose's around
keyword.
sub add_numbers {
return $_[1] + $_[2];
}
around add_numbers => signature(
method => !!1,
positional => [ Num, Num ],
goto_next => !!1,
package => __PACKAGE__,
subname => 'add_numbers',
);
say __PACKAGE__->add_numbers( 2, 3 ); # says 5
Note the way around
works in Moose is that it expects a wrapper coderef as its final argument. That wrapper coderef then expects to be given a reference to the original function as its first parameter.
This can allow, for example, a role to provide a signature wrapping a method defined in a class.
This is kind of complex, and you're unlikely to use it, but it's been proven useful for tools that integrate Type::Params with Moose-like method modifiers.
strictness
Bool|Str
If you set strictness
to a false value (0, undef, or the empty string), then certain signature checks will simply never be done. The initial check that there's the correct number of parameters, plus type checks on parameters which don't coerce can be skipped.
If you set it to a true boolean (i.e. 1) or do not set it at all, then these checks will always be done.
Alternatively, it may be set to the quoted fully-qualified name of a Perl global variable or a constant, and that will be compiled into the coderef as a condition to enable strict checks.
state $signature = signature(
strictness => '$::CHECK_TYPES',
positional => [ Int, ArrayRef ],
);
# Type checks are skipped
{
local $::CHECK_TYPES = 0;
my ( $number, $list ) = $signature->( {}, {} );
}
# Type checks are performed
{
local $::CHECK_TYPES = 1;
my ( $number, $list ) = $signature->( {}, {} );
}
A recommended use of this is with Devel::StrictMode.
use Devel::StrictMode qw( STRICT );
state $signature = signature(
strictness => STRICT,
positional => [ Int, ArrayRef ],
);
multiple
ArrayRef
This option allows your signature to support multiple calling conventions. Each entry in the array is an alternative signature, as a hashref:
state $signature = signature(
multiple => [
{
positional => [ ArrayRef, Int ],
},
{
named => [ array => ArrayRef, index => Int ],
named_to_list => 1,
},
],
);
That signature will allow your function to be called as:
your_function( $arr, $ix )
your_function( array => $arr, index => $ix )
your_function( { array => $arr, index => $ix } )
Sometimes the alternatives will return the parameters in a different order:
state $signature = signature(
multiple => [
{ positional => [ ArrayRef, Int ] },
{ positional => [ Int, ArrayRef ] },
],
);
my ( $xxx, $yyy ) = $signature->( @_ );
So how does your sub know whether $xxx
or $yyy
is the arrayref? One option is to use the ${^_TYPE_PARAMS_MULTISIG}
global variable which will be set to the index of the signature which was used:
my @results = $signature->( @_ );
my ( $arr, $ix ) = ${^_TYPE_PARAMS_MULTISIG} == 1
? reverse( @results )
: @results;
A neater solution is to use a goto_next
coderef to re-order alternative signature results into your preferred order:
state $signature = signature(
multiple => [
{ positional => [ ArrayRef, Int ] },
{ positional => [ Int, ArrayRef ], goto_next => sub { reverse @_ } },
],
);
my ( $arr, $ix ) = $signature->( @_ );
While conceptally multiple
is an arrayref of hashrefs, it is also possible to use arrayrefs in the arrayref.
multiple => [
[ ArrayRef, Int ],
[ Int, ArrayRef ],
]
When an arrayref is used like that, it is a shortcut for a positional signature.
Coderefs may additionally be used:
state $signature = signature(
multiple => [
[ ArrayRef, Int ],
{ positional => [ Int, ArrayRef ], goto_next => sub { reverse @_ } },
sub { ... },
sub { ... },
],
);
The coderefs should be subs which return a list of parameters if they succeed and throw an exception if they fail.
The following signatures are equivalent:
state $sig_1 = signature(
multiple => [
{ method => 1, positional => [ ArrayRef, Int ] },
{ method => 1, positional => [ Int, ArrayRef ] },
],
);
state $sig_2 = signature(
method => 1,
multiple => [
{ positional => [ ArrayRef, Int ] },
{ positional => [ Int, ArrayRef ] },
],
);
The multiple
option can also be abbreviated to multi
.
So signature( multi => [...] )
can be used instead of the longer signature( multiple => [...] )
. Three whole keystrokes saved!
(Note: in older releases of Type::Params, ${^_TYPE_PARAMS_MULTISIG}
was called ${^TYPE_PARAMS_MULTISIG}
. The latter name is no longer supported.)
message
Str
Only used by multiple
signatures. The error message to throw when no signatures match.
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.
bless
Bool|ClassName, class
ClassName|ArrayRef, and constructor
Str
Named parameters are usually returned as a blessed object:
sub add_numbers {
state $sig = signature( named => [ num1 => Num, num2 => Num ] );
my ( $arg ) = $sig->( @_ );
return $arg->num1 + $arg->num2;
}
The class they are blessed into is one built on-the-fly by Type::Params. However, these three signature options allow you more control over that process.
Firstly, if you set bless => false
and do not set class
or constructor
, then $arg
will just be an unblessed hashref.
sub add_numbers {
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
bless => !!0,
);
my ( $arg ) = $sig->( @_ );
return $arg->{num1} + $arg->{num2};
}
This is a good speed boost, but having proper methods for each named parameter is a helpful way to catch misspelled names.
If you wish to manually create a class instead of relying on Type::Params generating one on-the-fly, you can do this:
package Params::For::AddNumbers {
sub num1 { return $_[0]{num1} }
sub num2 { return $_[0]{num2} }
sub sum {
my $self = shift;
return $self->num1 + $self->num2;
}
}
sub add_numbers {
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
bless => 'Params::For::AddNumbers',
);
my ( $arg ) = $sig->( @_ );
return $arg->sum;
}
Note that Params::For::AddNumbers
here doesn't include a new
method because Type::Params will directly do bless( $arg, $opts{bless} )
.
If you want Type::Params to use a proper constructor, you should use the class
option instead:
package Params::For::AddNumbers {
use Moo;
has [ 'num1', 'num2' ] => ( is => 'ro' );
sub sum {
my $self = shift;
return $self->num1 + $self->num2;
}
}
sub add_numbers {
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
class => 'Params::For::AddNumbers',
);
my ( $arg ) = $sig->( @_ );
return $arg->sum;
}
If you wish to use a constructor named something other than new
, then use:
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
class => 'Params::For::AddNumbers',
constructor => 'new_from_hashref',
);
Or as a shortcut:
state $sig = signature(
named => [ num1 => Num, num2 => Num ],
class => [ 'Params::For::AddNumbers', 'new_from_hashref' ],
);
It is doubtful you want to use any of these options, except bless => false
.
returns
TypeTiny, returns_scalar
TypeTiny, and returns_list
TypeTiny
These can be used to specify the type returned by your function.
sub round_number {
state $sig = signature(
pos => [ Num ],
returns => Int,
);
my ( $num ) = $sig->( @_ );
return int( $num );
}
If your function returns different types in scalar and list context, you can use returns_scalar
and returns_list
to indicate separate return types in different contexts.
state $sig = signature(
pos => [ Int, Int ],
returns_scalar => Int,
returns_list => Tuple[ Int, Int, Int ],
);
The returns_list
constraint is defined using an ArrayRef-like or HashRef-like type constraint even though it's returning a list, not a single reference.
If your function is called in void context, then its return value is unimportant and should not be type checked.
Note: because signature checks happen early before the rest of your function executes, the returns
, returns_scalar
, and returns_list
options are considered advisorary and for documentation and are not actually checked! However, the signature_for
keyword, which wraps your entire sub, is able to check them.
Parameter Options
In the parameter lists for the positional
and named
signature options, each parameter may be followed by a hashref of options specific to that parameter:
signature(
positional => [
Int, \%options_for_first_parameter,
Int, \%options_for_other_parameter,
],
%more_options_for_signature,
);
signature(
named => [
foo => Int, \%options_for_foo,
bar => Int, \%options_for_bar,
],
%more_options_for_signature,
);
The following options are supported for parameters.
optional
Bool
An option called optional!
This makes a parameter optional:
sub add_nums {
state $sig = signature(
positional => [
Int,
Int,
Bool, { optional => !!1 },
],
);
my ( $num1, $num2, $debug ) = $sig->( @_ );
my $sum = $num1 + $num2;
warn "$sum = $num1 + $num2" if $debug;
return $sum;
}
add_nums( 2, 3, 1 ); # prints warning
add_nums( 2, 3, 0 ); # no warning
add_nums( 2, 3 ); # no warning
Types::Standard also provides a Optional parameterizable type which may be a neater way to do this:
state $sig = signature(
positional => [ Int, Int, Optional[Bool] ],
);
In signatures with positional parameters, any optional parameters must be defined after non-optional parameters. The tail
option provides a workaround for required parameters at the end of @_
.
In signatures with named parameters, the order of optional and non-optional parameters is unimportant.
slurpy
Bool
A signature may contain a single slurpy parameter, which mops up any other arguments the caller provides your function.
In signatures with positional parameters, slurpy params must always have some kind of ArrayRef or HashRef type constraint, must always appear at the end of the list of positional parameters, and they work like this:
sub add_nums {
state $sig = signature(
positional => [
Num,
ArrayRef[Num], { slurpy => !!1 },
],
);
my ( $first_num, $other_nums ) = $sig->( @_ );
my $sum = $first_num;
$sum += $_ for @$other_nums;
return $sum;
}
say add_nums( 1 ); # says 1
say add_nums( 1, 2 ); # says 3
say add_nums( 1, 2, 3 ); # says 6
say add_nums( 1, 2, 3, 4 ); # says 10
In signatures with named parameters, slurpy params must always have some kind of HashRef type constraint, and they work like this:
use builtin qw( true false );
sub process_data {
state $sig = signature(
method => true,
named => [
input => FileHandle,
output => FileHandle,
flags => HashRef[Bool], { slurpy => true },
],
);
my ( $self, $arg ) = @_;
warn "Beginning data processing" if $arg->flags->{debug};
...;
}
$widget->process_data(
input => \*STDIN,
output => \*STDOUT,
debug => true,
);
The Slurpy type constraint from Types::Standard may be used as a shortcut to specify slurpy parameters:
signature(
positional => [ Num, Slurpy[ ArrayRef[Num] ] ],
)
The type Slurpy[Any] is handled specially and treated as a slurpy ArrayRef in signatures with positional parameters, and a slurpy HashRef in signatures with named parameters, but has some additional optimizations for speed.
default
CodeRef|ScalarRef|Ref|Str|Undef
A default may be provided for a parameter.
state $check = signature(
positional => [
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 = signature(
positional => [
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.
Instead of a coderef, you can use a reference to a string of Perl source code:
state $check = signature(
positional => [
Int,
Int, { default => \ '6 * 111' },
Int, { default => \ '9 * 111' },
],
);
Defaults will be validated against the type constraint, and potentially coerced.
Any parameter with a default will automatically be optional.
Note that having any defaults in a signature (even if they never end up getting used) can slow it down, as Type::Params will need to build a new array instead of just returning @_
.
coerce
Bool
Speaking of which, the coerce
option allows you to indicate that a value should be coerced into the correct type:
state $sig = signature(
positional => [
Int,
Int,
Bool, { coerce => true },
],
);
Setting coerce
to false will disable coercion.
If coerce
is not specified, so is neither true nor false, then coercion will be enabled if the type constraint has a coercion, and disabled otherwise.
Note that having any coercions in a signature (even if they never end up getting used) can slow it down, as Type::Params will need to build a new array instead of just returning @_
.
clone
Bool
If this is set to true, it will deep clone incoming values via dclone
from Storable (a core module since Perl 5.7.3).
In the below example, $arr
is a reference to a clone of @numbers
, so pushing additional numbers to it leaves @numbers
unaffected.
sub foo {
state $check = signature(
positional => [
ArrayRef, { clone => 1 }
],
);
my ( $arr ) = &$check;
push @$arr, 4, 5, 6;
}
my @numbers = ( 1, 2, 3 );
foo( \@numbers );
print "@numbers\n"; ## 1 2 3
Note that cloning will significantly slow down your signature.
name
Str
This overrides the name of a named parameter. I don't know why you would want to do that.
The following signature has two parameters: foo
and bar
. The name fool
is completely ignored.
signature(
named => [
fool => Int, { name => 'foo' },
bar => Int,
],
)
You can, however, also name positional parameters, which don't usually have names.
signature(
positional => [
Int, { name => 'foo' },
Int, { name => 'bar' },
],
)
The names of positional parameters are not really used for anything at the moment, but may be incorporated into error messages or similar in the future.
getter
Str
For signatures with named parameters, specifies the method name used to retrieve this parameter's value from the $arg
object.
sub process_data {
state $sig = signature(
method => true,
named => [
input => FileHandle, { getter => 'in' },
output => FileHandle, { getter => 'out' },
flags => HashRef[Bool], { slurpy => true },
],
);
my ( $self, $arg ) = @_;
warn "Beginning data processing" if $arg->flags->{debug};
my ( $in, $out ) = ( $arg->in, $arg->out );
...;
}
$widget->process_data(
input => \*STDIN,
output => \*STDOUT,
debug => true,
);
Ignored by signatures with positional parameters.
predicate
Str
The $arg
object provided by signatures with named parameters will also include "has" methods for any optional arguments. For example:
state $sig = signature(
method => true,
named => [
input => Optional[ FileHandle ],
output => Optional[ FileHandle ],
flags => Slurpy[ HashRef[Bool] ],
],
);
my ( $self, $arg ) = $sig->( @_ );
if ( $self->has_input and $self->has_output ) {
...;
}
Setting a predicate
option allows you to choose a different name for this method.
It is also possible to set a predicate
for non-optional parameters, which don't normally get a "has" method.
Ignored by signatures with positional parameters.
alias
Str|ArrayRef[Str]
A list of alternative names for the parameter, or a single alternative name.
sub add_numbers {
state $sig = signature(
named => [
first_number => Int, { alias => [ 'x' ] },
second_number => Int, { alias => 'y' },
],
);
my ( $arg ) = $sig->( @_ );
return $arg->first_number + $arg->second_number;
}
say add_numbers( first_number => 40, second_number => 2 ); # 42
say add_numbers( x => 40, y => 2 ); # 42
say add_numbers( first_number => 40, y => 2 ); # 42
say add_numbers( first_number => 40, x => 1, y => 2 ); # dies!
Ignored by signatures with positional parameters.
strictness
Bool|Str
Overrides the signature option strictness
on a per-parameter basis.
signature_for $function_name => ( %spec )
Like signature
, but instead of returning a coderef, wraps an existing function, so you don't need to deal with the mechanics of generating the signature at run-time, calling it, and extracting the returned values.
The following three examples are roughly equivalent:
sub add_nums {
state $signature = signature(
positional => [ Num, Num ],
);
my ( $x, $y ) = $signature->( @_ );
return $x + $y;
}
Or:
signature_for add_nums => (
positional => [ Num, Num ],
);
sub add_nums {
my ( $x, $y ) = @_;
return $x + $y;
}
Or since Perl 5.20:
signature_for add_nums => (
positional => [ Num, Num ],
);
sub add_nums ( $x, $y ) {
return $x + $y;
}
The signature_for
keyword turns signature
inside-out.
As of 2024, you probably want to be using signature_for
instead of signature
.
The same signature specification options are supported, with the exception of want_source
, want_details
, and goto_next
which will not work. (If using the multiple
option, then goto_next
is still supported in the nested signatures.)
The returns
, returns_scalar
, and returns_list
options are actually checked instead of just being advisorary. (Because this means that the signature will need to run code *after* your original function has run, it means the signature will be visible on the caller stack from within your function.)
If you are providing a signature for a sub in another package, then signature_for "Some::Package::some_sub" => ( ... )
will work, as will signature_for some_sub => ( package => "Some::Package", ... )
. If method
is true, then signature_for
will respect inheritance when determining which sub to wrap. signature_for
will not be able to find lexical subs, so use signature
within the sub instead.
The goto_next
option is what signature_for
uses to "connect" the signature to the body of the sub, so do not use it unless you understand the consequences and want to override the normal behaviour.
If the sub being wrapped cannot be found, then signature_for
will usually throw an error. If you want it to "work" in this situation, use the fallback
option. fallback => \&alternative_coderef_to_wrap
will instead wrap a different coderef if the original cannot be found. fallback => 1
is a shortcut for fallback => sub {}
. An example where this might be useful is if you're adding signatures to methods which are inherited from a parent class, but you are not 100% confident will exist (perhaps dependent on the version of the parent class).
signature_for add_nums => (
positional => [ Num, Num ],
fallback => sub { $_[0] + $_[1] },
);
signature_for( \@functions, %opts )
is a useful shortcut if you have multiple functions with the same signature.
signature_for [ 'add_nums', 'subtract_nums' ] => (
positional => [ Num, Num ],
);
signature_for
does return a value.
my $meta = signature_for add_nums => (
positional => [ Num, Num ],
);
sub add_nums ( $x, $y ) {
return $x + $y;
}
Or when used with multiple functions:
my @metas = signature_for [ 'add_nums', 'subtract_nums' ] => (...);
This is a blessed Type::Params::Signature object which provides some introspection possibilities.
LEGACY API
The following functions were the API prior to Type::Params v2. They are still supported, but their use is now discouraged.
If you don't provide an import list at all, you will import compile
and compile_named
:
use Type::Params;
This does the same:
use Type::Params -v1;
The following exports compile
, compile_named
, and compile_named_oo
:
use Type::Params -compile;
The following exports wrap_subs
and wrap_methods
:
use Type::Params -wrap;
compile( @pos_params )
Equivalent to signature( positional => \@pos_params )
.
compile( \%spec, @pos_params )
is equivalent to signature( %spec, positional => \@pos_params )
.
compile_named( @named_params )
Equivalent to signature( bless => 0, named => \@named_params )
.
compile_named( \%spec, @named_params )
is equivalent to signature( bless => 0, %spec, named => \@named_params )
.
compile_named_oo( @named_params )
Equivalent to signature( bless => 1, named => \@named_params )
.
compile_named_oo( \%spec, @named_params )
is equivalent to signature( bless => 1, %spec, named => \@named_params )
.
validate( \@args, @pos_params )
Equivalent to signature( positional => \@pos_params )->( @args )
.
The validate
function has never been recommended, and is not exported unless requested by name.
validate_named( \@args, @named_params )
Equivalent to signature( bless => 0, named => \@named_params )->( @args )
.
The validate_named
function has never been recommended, and is not exported unless requested by name.
wrap_subs( func1 => \@params1, func2 => \@params2, ... )
Equivalent to:
signature_for func1 => ( positional => \@params1 );
signature_for func2 => ( positional => \@params2 );
One slight difference is that instead of arrayrefs, you can provide the output of one of the compile
functions:
wrap_subs( func1 => compile_named( @params1 ) );
wrap_subs
is not exported unless requested by name.
wrap_methods( func1 => \@params1, func2 => \@params2, ... )
Equivalent to:
signature_for func1 => ( method => 1, positional => \@params1 );
signature_for func2 => ( method => 1, positional => \@params2 );
One slight difference is that instead of arrayrefs, you can provide the output of one of the compile
functions:
wrap_methods( func1 => compile_named( @params1 ) );
wrap_methods
is not exported unless requested by name.
multisig( @alternatives )
Equivalent to:
signature( multiple => \@alternatives )
multisig( \%spec, @alternatives )
is equivalent to signature( %spec, multiple => \@alternatives )
.
TYPE CONSTRAINTS
Although Type::Params is not a real type library, it exports two type constraints. Their use is no longer recommended.
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 $check = signature(
method => Invocant,
positional => [ ArrayRef, Int ],
);
my ($self_or_class, $arr, $ix) = $check->(@_);
return $arr->[ $ix ];
}
Invocant
is not exported unless requested by name.
Recommendation: use Defined from Types::Standard instead.
ArgsObject
Type::Params exports a parameterizable type constraint ArgsObject. It accepts the kinds of objects returned by signature checks for named parameters.
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 'signature';
sub bar {
state $check = signature(
named => [
xxx => Int,
yyy => ArrayRef,
],
);
my ( $got ) = $check->( @_ );
return 'Foo'->new( args => $got );
}
}
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.
ArgsObject
is not exported unless requested by name.
Recommendation: use Object from Types::Standard instead.
ENVIRONMENT
PERL_TYPE_PARAMS_XS
-
Affects the building of accessors for
$arg
objects. 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 Class::XSAccessor is not installed or is too old, pure Perl will always be used as a fallback.
BUGS
Please report any bugs to https://github.com/tobyink/p5-type-tiny/issues.
SEE ALSO
Type::Tiny, Type::Coercion, Types::Standard.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2013-2014, 2017-2024 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.