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.\" ========================================================================
.\"
.IX Title "Type::Tie 3"
.TH Type::Tie 3 "2020-11-18" "perl v5.26.3" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Type::Tie \- tie a variable to a type constraint
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
Type::Tie is a response to this sort of problem...
.PP
.Vb 2
\&   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 => \e@N);
\&   
\&   # Everything OK so far...
\&   
\&   # Now watch this!
\&   push @N, "Monkey!";
\&   print $object\->dump;
\&   
\&   # Houston, we have a problem!
.Ve
.PP
Just declare \f(CW@N\fR like this:
.PP
.Vb 2
\&   use Type::Tie;
\&   use Types::Standard qw( Num );
\&   
\&   ttie my @N, Num, ( 1, 2, 3, 3.14159 );
.Ve
.PP
Now any attempt to add a non-numeric value to \f(CW@N\fR will die.
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module exports a single function: \f(CW\*(C`ttie\*(C'\fR. \f(CW\*(C`ttie\*(C'\fR 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.
.PP
.Vb 2
\&   use Type::Tie;
\&   use Types::Standard qw( Int Num );
\&   
\&   ttie my $count, Int\->plus_coercions(Num, \*(Aqint $_\*(Aq), 0;
\&   
\&   $count++;            # ok
\&   $count = 2;          # ok
\&   $count = 3.14159;    # ok, coerced to 3
\&   $count = "Monkey!";  # dies
.Ve
.PP
While the examples in documentation (and the test suite) show type
constraints from Types::Standard, but any type constraint objects
supporting the Type::API interfaces should work. This includes:
.IP "\(bu" 4
Moose::Meta::TypeConstraint / MooseX::Types
.IP "\(bu" 4
Mouse::Meta::TypeConstraint / MouseX::Types
.IP "\(bu" 4
Specio
.IP "\(bu" 4
Type::Tiny
.SS "About Cloning with Storage::dclone (and Clone::clone)"
.IX Subsection "About Cloning with Storage::dclone (and Clone::clone)"
Cloning variables with Storage::dclone works, but cloning with Clone::clone is
not possible. See
Bug #127576 for Type-Tie: Doesn't work with Clone::clone <https://rt.cpan.org/Public/Bug/Display.html?id=127576>
.SH "BUGS"
.IX Header "BUGS"
Please report any bugs to
<http://rt.cpan.org/Dist/Display.html?Queue=Type\-Tie>.
.SH "SUPPORT"
.IX Header "SUPPORT"
\&\fB\s-1IRC:\s0\fR support is available through in the \fI#moops\fR channel
on irc.perl.org <http://www.irc.perl.org/channels.html>.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Type::API,
Type::Utils,
Moose::Manual::Types,
MooseX::Lexical::Types.
.SH "AUTHOR"
.IX Header "AUTHOR"
Toby Inkster <tobyink@cpan.org>.
.SH "COPYRIGHT AND LICENCE"
.IX Header "COPYRIGHT AND LICENCE"
This software is copyright (c) 2013\-2014, 2018\-2019 by Toby Inkster.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
.SH "DISCLAIMER OF WARRANTIES"
.IX Header "DISCLAIMER OF WARRANTIES"
\&\s-1THIS PACKAGE IS PROVIDED \*(L"AS IS\*(R" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.\s0