Provided by: libtype-tiny-perl_1.016008-1_all 
NAME
Type::Tiny::Manual::Params - advanced information on Type::Params
MANUAL
To get started with Type::Params, please read Type::Tiny::Manual::UsingWithMoo which will
cover a lot of the basics, even if you're not using Moo.
"validate" and "validate_named"
The generally recommended way of using Type::Params is this:
sub mysub {
state $check = compile( SIGNATURE );
my @args = $check->( @_ );
}
But it is possible to do it in one call:
sub mysub {
my @args = validate( \@_, SIGNATURE );
}
There is also a "validate_named" function which acts as a counterpart for "compile_named".
This will generally be slower and less efficient than using "compile" first because
Type::Tiny can do a lot of optimizations in that first stage to make the second stage a
lot faster. (And the results of "compile" get stored in the "state" variable so that only
has to happen once.)
There is rarely a reason to use "validate" and "validate_named", but they exist if you
want them.
"multisig"
Multisig allows you to allow multiple ways of calling a sub.
sub repeat_string {
state $check = multisig(
compile(
Int,
Str,
),
compile_named(
{ named_to_list => 1 },
count => Int,
string => Str,
),
);
my ($count, $string) = $check->(@_);
return $string x $count;
}
repeat_string( "Hello", 42 ); # works
repeat_string( string => "Hello", count => 42 ); # works
repeat_string({ string => "Hello", count => 42 }); # works
repeat_string( qr/hiya/ ); # dies
It combines multiple checks and tries each until one works.
"wrap_subs" and "wrap_methods"
"wrap_subs" turns the "compile" idea inside out.
Instead of this:
sub foobar {
state $check = compile(Int, Str);
my ($foo, $bar) = @_;
...;
}
You do this:
sub foobar {
my ($foo, $bar) = @_;
...;
}
wrap_subs foobar => [ Int, Str ];
Or this:
sub foobar {
my ($foo, $bar) = @_;
...;
}
wrap_subs foobar => compile( Int, Str );
Mixed Named and Positional Parameters
This can be faked using positional parameters and a Slurpy dictionary.
state $check = compile(
Int,
Slurpy[
Dict[
foo => Int,
bar => Optional[Int],
baz => Optional[Int],
],
],
);
@_ = (42, foo => 21); # ok
@_ = (42, foo => 21, bar => 84); # ok
@_ = (42, foo => 21, bar => 10.5); # not ok
@_ = (42, foo => 21, quux => 84); # not ok
From Type::Params 1.009_002, "head" and "tail" options are accepted, which provide another
option for mixed named and positional arguments:
state $check = compile_named(
{ head => [ Int ] },
foo => Int,
bar => Optional[Int],
baz => Optional[Int],
],
);
The "head" is shifted off @_ before @_ is considered as a hash. The "tail" is popped off
@_ before @_ is considered as a hash.
Proper Signatures
Don't you wish your subs could look like this?
sub set_name (Object $self, Str $name) {
$self->{name} = $name;
}
Well; here are a few solutions for sub signatures that work with Type::Tiny...
Zydeco
Zydeco is a Perl OO syntax toolkit with Type::Tiny support baked in throughout.
package MyApp {
use Zydeco;
class Person {
has name ( type => Str );
method rename (Str $new_name) {
printf("%s will now be called %s\n", $self->name, $new_name);
$self->name($new_name);
}
coerce from Str via {
$class->new(name => $_)
}
}
class Company {
has owner ( type => 'Person' );
}
}
my $acme = MyApp->new_company(owner => "Robert");
$acme->owner->rename("Bob");
Kavorka
Kavorka is a sub signatures implementation written to natively use Type::Utils'
"dwim_type" for type constraints, and take advantage of Type::Tiny's features such as
inlining, and coercions.
method set_name (Str $name) {
$self->{name} = $name;
}
Kavorka's signatures provide a lot more flexibility, and slightly more speed than
Type::Params. (The speed comes from inlining almost all type checks into the body of the
sub being declared.)
Kavorka also includes support for type checking of the returned value.
Kavorka can also be used as part of Moops, a larger framework for object oriented
programming in Perl.
Function::Parameters
Function::Parameters offers support for Type::Tiny and MooseX::Types.
use Types::Standard qw( Str );
use Function::Parameters;
method set_name (Str $name) {
$self->{name} = $name;
}
Attribute::Contract
Both Kavorka and Function::Parameters require a relatively recent version of Perl.
Attribute::Contract supports older versions by using a lot less magic.
You want Attribute::Contract 0.03 or above.
use Attribute::Contract -types => [qw/Object Str/];
sub set_name :ContractRequires(Object, Str) {
my ($self, $name) = @_;
$self->{name} = $name;
}
Attribute::Contract also includes support for type checking of the returned value.
Type::Params versus X
Params::Validate
Type::Params is not really a drop-in replacement for Params::Validate; the API differs far
too much to claim that. Yet it performs a similar task, so it makes sense to compare them.
• Type::Params will tend to be faster if you've got a sub which is called repeatedly,
but may be a little slower than Params::Validate for subs that are only called a few
times. This is because it does a bunch of work the first time your sub is called to
make subsequent calls a lot faster.
• Params::Validate doesn't appear to have a particularly natural way of validating a mix
of positional and named parameters.
• Type::Utils allows you to coerce parameters. For example, if you expect a Path::Tiny
object, you could coerce it from a string.
• If you are primarily writing object-oriented code, using Moose or similar, and you are
using Type::Tiny type constraints for your attributes, then using Type::Params allows
you to use the same constraints for method calls.
• Type::Params comes bundled with Types::Standard, which provides a much richer
vocabulary of types than the type validation constants that come with
Params::Validate. For example, Types::Standard provides constraints like
"ArrayRef[Int]" (an arrayref of integers), while the closest from Params::Validate is
"ARRAYREF", which you'd need to supplement with additional callbacks if you wanted to
check that the arrayref contained integers.
Whatsmore, Type::Params doesn't just work with Types::Standard, but also any other
Type::Tiny type constraints.
Params::ValidationCompiler
Params::ValidationCompiler does basically the same thing as Type::Params.
• Params::ValidationCompiler and Type::Params are likely to perform fairly similarly. In
most cases, recent versions of Type::Params seem to be slightly faster, but except in
very trivial cases, you're unlikely to notice the speed difference. Speed probably
shouldn't be a factor when choosing between them.
• Type::Params's syntax is more compact:
state $check = compile(Object, Optional[Int], Slurpy[ArrayRef]);
Versus:
state $check = validation_for(
params => [
{ type => Object },
{ type => Int, optional => 1 },
{ type => ArrayRef, slurpy => 1 },
],
);
• Params::ValidationCompiler probably has slightly better exceptions.
NEXT STEPS
Here's your next step:
• Type::Tiny::Manual::NonOO
Type::Tiny in non-object-oriented code.
AUTHOR
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE
This software is copyright (c) 2013-2014, 2017-2022 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.