oracular (3) Type::Tie.3pm.gz

NAME

       Type::Tie - tie a variable to a type constraint

SYNOPSIS

       Type::Tie is a response to this sort of problem...

          use strict;
          use warnings;

          {
             package Local::Testing;
             use Moose;
             has numbers => ( is => "ro", isa => "ArrayRef[Num]" );
          }

          # Nice list of numbers.
          my @N = ( 1, 2, 3, 3.14159 );

          # Create an object with a reference to that list.
          my $object = Local::Testing->new(numbers => \@N);

          # Everything OK so far...

          # Now watch this!
          push @N, "Monkey!";
          print $object->dump;

          # Houston, we have a problem!

       Just declare @N like this:

          use Type::Tie;
          use Types::Standard qw( Num );

          ttie my @N, Num, ( 1, 2, 3, 3.14159 );

       Now any attempt to add a non-numeric value to @N will die.

DESCRIPTION

       This module exports a single function: "ttie". "ttie" ties a variable to a type constraint, ensuring that
       whatever values stored in the variable will conform to the type constraint. If the type constraint has
       coercions, these will be used if necessary to ensure values assigned to the variable conform.

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

          ttie my $count, Int->plus_coercions(Num, 'int $_'), 0;

          print tied($count)->type, "\n";   # 'Int'

          $count++;            # ok
          $count = 2;          # ok
          $count = 3.14159;    # ok, coerced to 3
          $count = "Monkey!";  # dies

       While the examples in documentation (and the test suite) show type constraints from Types::Standard, any
       type constraint objects supporting the Type::API interfaces should work. This includes:

       •   Moose::Meta::TypeConstraint / MooseX::Types

       •   Mouse::Meta::TypeConstraint / MouseX::Types

       •   Specio

       •   Type::Tiny

       However, with Type::Tiny, you don't even need to "use Type::Tie".

          use Types::Standard qw( Int Num );

          tie my $count, Int->plus_coercions(Num, 'int $_'), 0;

          print tied($count)->type, "\n";   # 'Int'

          $count++;            # ok
          $count = 2;          # ok
          $count = 3.14159;    # ok, coerced to 3
          $count = "Monkey!";  # dies

   Cloning tied variables
       If you clone tied variables with "dclone" from Storable, the clone will also be tied. The Clone module is
       also able to successfully clone tied variables. With other cloning techniques, your level of success may
       vary.

BUGS

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

SEE ALSO

       Type::API, Type::Tiny, Type::Utils, Moose::Manual::Types, MooseX::Lexical::Types.

AUTHOR

       Toby Inkster <tobyink@cpan.org>.

COPYRIGHT AND LICENCE

       This software is copyright (c) 2013-2014, 2018-2019, 2022-2023 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.