Validating parameters

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.

multiple

The multiple option allows you to specify multiple ways of calling a sub. 

 sub repeat_string {
   state $check = signature(
     multiple => [
       { positional => [ Str, Int ] },
       { named => [ string => Str, count => Int ], named_to_list => 1 },
     ],
   );
   
   my ( $string, $count ) = $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.

signature_for

signature_for turns signature inside out.

Instead of this: 

 sub foobar {
   state $check = signature( positional => [ Int, Str ] );
   my ( $foo, $bar ) = $check->( @_ );
   ...;
 }

You do this: 

 signature_for foobar => (
   positional => [ Int, Str ],
 );
 
 sub foobar {
   my ( $foo, $bar ) = @_;
   ...;
 }

Or in Perl 5.20+, you can even do this: 

 signature_for foobar => (
   positional => [ Int, Str ],
 );
 
 sub foobar ( $foo, $bar ) {
   ...;
 }

Functions versus Methods

For subs which are intended to be called as functions: 

 signature( method => 0, ... );
 signature( ... );                       # this is the default anyway

For subs which are intended to be called as methods on a blessed object: 

 signature( method => Object, ... );

And for subs which are intended to be called as methods on a class: 

 signature( method => ClassName, ... );
 signature( method => Str, ... );        # less readable, but faster check!

The following is also allowed, which indicates that the sub is intended to be called as a method, but you don't want to do type checks on the invocant: 

 signature( method => 1, ... );

Mixed Named and Positional Parameters

The head and tail options allow required positional parameters at the start or end of a named parameter list: 

 state $check = signature(
   head  => [ Int ],
   named => [
     foo => Int,
     bar => Optional[Int],
     baz => Optional[Int],
   ],
 );
 
 $check->( 42, foo => 21 );                 # ok
 $check->( 42, foo => 21, bar  => 84 );     # ok
 $check->( 42, foo => 21, bar  => 10.5 );   # not ok
 $check->( 42, foo => 21, quux => 84 );     # not ok

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.

Params::ValidationCompiler

Params::ValidationCompiler does basically the same thing as Type::Params .

Next Steps

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