/ 
Type-Params-0.000_01
/ Type::Params

NAME

Type::Params - Params::Validate-like parameter validation using Type::Tiny type constraints and coercions

SYNOPSIS

use v5.10;
use strict;
use warnings;

use Type::Params qw( compile );
use Types::Standard qw( slurpy Str ArrayRef Num );
  
sub deposit_monies
{
   state $check = compile( Str, Str, slurpy ArrayRef[Num] );
   my ($sort_code, $account_number, $monies) = $check->(@_);
   
   my $account = Local::BankAccount->new($sort_code, $account_number);
   $account->deposit($_) for @$monies;
}

deposit_monies("12-34-56", "11223344", 1.2, 3, 99.99);

DESCRIPTION

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 $deposit_monies_check;
sub deposit_monies
{
   $deposit_monies_check ||= compile( Str, Str, slurpy ArrayRef[Num] );
   my ($sort_code, $account_number, $monies) = $check->(@_);
   
   ...;
}

Not quite as neat, but not awful either.

There's a shortcut reducing it to one step:

use Type::Params qw( validate );

sub deposit_monies
{
   my ($sort_code, $account_number, $monies) = 
      validate( \@_, Str, Str, slurpy ArrayRef[Num] );
   
   ...;
}

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.

COOKBOOK

Positional Parameters

sub nth_root
{
   state $check = compile( Num, Num );
   my ($x, $n) = $check->(@_);
   
   return $x ** (1 / $n);
}

Method Calls

use Types::Standard qw( ClassName Object Str Int );

# a class method
sub new_from_json
{
   state $check = compile( ClassName, Str );
   my ($class, $json) = $check->(@_);
   
   $class->new( from_json($json) );
}

# an object method
sub dump
{
   state $check = compile( Object, Int );
   my ($self, $limit) = $check->(@_);
   
   local $Data::Dumper::Maxdepth = $limit;
   print Data::Dumper::Dumper($self);
}

# can be called as either
sub run
{
   state $check = compile( Object | ClassName );
   my ($proto) = $check->(@_);
   
   my $self = ref($proto) ? $proto : $default_instance;
   $self->_run;
}

Optional Parameters

use Types::Standard qw( Object Optional Int );

sub dump
{
   state $check = compile( Object, Optional[Int] );
   my ($self, $limit) = $check->(@_);
   $limit //= 0;
   
   local $Data::Dumper::Maxdepth = $limit;
   print Data::Dumper::Dumper($self);
}

$obj->dump(1);      # ok
$obj->dump();       # ok
$obj->dump(undef);  # dies

Slurpy Parameters

use Types::Standard qw( slurpy ClassName HashRef );

sub new
{
   state $check = compile( ClassName, slurpy HashRef );
   my ($class, $ref) = $check->(@_);
   bless $ref => $class;
}

__PACKAGE__->new(foo => 1, bar => 2);

The following types from Types::Standard can be made slurpy: ArrayRef, Tuple, HashRef, Map, Dict. Hash-like types will die if an odd number of elements are slurped in.

A check may only have one slurpy parameter, and it must be the last parameter.

Named Parameters

Just use a slurpy Dict:

use Types::Standard qw( slurpy Dict Ref Optional Int );

sub dump
{
   state $check = compile(
      slurpy Dict[
         var    => Ref,
         limit  => Optional[Int],
      ],
   );
   my ($arg) = $check->(@_);
   
   local $Data::Dumper::Maxdepth = $arg->{limit};
   print Data::Dumper::Dumper($arg->{var});
}

dump(var => $foo, limit => 1);   # ok
dump(var => $foo);               # ok
dump(limit => 1);                # dies

Mixed Positional and Named Parameters

use Types::Standard qw( slurpy Dict Ref Optional Int );

sub my_print
{
   state $check = compile(
      Str,
      slurpy Dict[
         colour => Optional[Str],
         size   => Optional[Int],
      ],
   );
   my ($string, $arg) = $check->(@_);
}

my_print("Hello World", colour => "blue");

Coercions

Coercions will automatically be applied for all type constraints that have a coercion associated.

use Type::Utils;
use Types::Standard qw( Int Num );

my $RoundedInt = declare as Int;
coerce $RoundedInt, from Num, via q{ int($_) };

sub set_age
{
   state $check = compile( Object, $RoundedInt );
   my ($self, $age) = $check->(@_);
   
   $self->{age} = $age;
}

$obj->set_age(32.5);   # ok; coerced to "32".

Coercions carry over into structured types such as ArrayRef automatically:

sub delete_articles
{
   state $check = compile( Object, slurpy ArrayRef[$RoundedInt] );
   my ($db, $articles) = $check->(@_);
   
   $db->select_article($_)->delete for @$articles;
}

# delete articles 1, 2 and 3
delete_articles($my_db, 1.1, 2.2, 3.3);

If type Foo has coercions from Str and ArrayRef and you want to prevent coercion, then use:

state $check = compile( Foo->no_coercions );

Or if you just want to prevent coercion from Str, use:

state $check = compile( Foo->minus_coercions(Str) );

Or maybe add an extra coercion:

state $check = compile(
   Foo->plus_coercions(Int, q{ Foo->new_from_number($_) }),
);

Note that the coercion is specified as a string of Perl code. This is usually the fastest way to do it, but a coderef is also accepted. Either way, the value to be coerced is $_.

BUGS

Please report any bugs to http://rt.cpan.org/Dist/Display.html?Queue=Type-Params.

SEE ALSO

Type::Tiny, Type::Coercion, Types::Standard.

AUTHOR

Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

This software is copyright (c) 2013 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.