NAME¶
Type::Tiny::Manual::Params - coerce and validate arguments to functions and
methods
DESCRIPTION¶
There is a module called Type::Params available to wrap up type coercion and
constraint checks into a single, simple and fast check. If you care about
speed, and your sub signatures are fairly simple, then this is the way to
go...
use feature qw( state );
use Types::Standard qw( Str );
use Type::Utils;
use Type::Params qw( compile );
my $Invocant = class_type { class => __PACKAGE__ };
sub set_name
{
state $check = compile($Invocant, Str);
my ($self, $name) = $check->(@_);
...;
}
See the COOKBOOK section of Type::Params for further information.
The Somewhat More Manual Way...¶
In general, Type::Params should be sufficient to cover most needs, and will
probably run faster than almost anything you could cook up yourself. However,
sometimes you need to deal with unusual function signatures that it does not
support. For example, imagine function "format_string" takes an
optional hashref of formatting instructions, followed by a required string.
You might expect to be able to handle it like this:
sub format_string
{
state $check = compile(Optional[HashRef], Str);
my ($instructions, $string) = $check->(@_);
...;
}
However, this won't work, as Type::Params expects required parameters to always
precede optional ones. So there are times you need to handle parameters more
manually.
In these cases, bear in mind that for any type constraint object you have
several useful checking methods available:
Str->check($var) # returns a boolean
is_Str($var) # ditto
Str->($var) # returns $var or dies
assert_Str($var) # ditto
Here's how you might handle the "format_string" function:
sub format_string
{
my $instructions;
$instructions = shift if HashRef->check($_[0]);
my $string = Str->(shift);
...;
}
Alternatively, you could manipulate @_ before passing it to the compiled check:
sub format_string
{
state $check = compile(HashRef, Str);
my ($instructions, $str) = $check->(@_==1 ? ({}, @_) : @_);
...;
}
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...
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} = $name;
}
Kavorka's signatures provide a lot more flexibility, and slightly more speed
than Type::Params. (The speed comes from inlining almost all type checks into
the body of the sub being declared.)
Kavorka also includes support for type checking of the returned value.
Kavorka can also be used as part of Moops, a larger framework for object
oriented programming in Perl.
Function::Parameters
The following should work with Function::Parameters 1.0201 or above:
use Type::Utils;
use Function::Parameters {
method => {
strict => 1,
reify_type => sub { Type::Utils::dwim_type($_[0]) },
},
};
method set_name (Str $name)
{
$self->{name} = $name;
}
Note that by default, Function::Parameters uses Moose's type constraints. The
"reify_type" option above (introduced in Function::Parameters
1.0201) allows you to "divert" type constraint lookups. Using
Type::Tiny constraints will gain you about a 7% speed-up in function signature
checks.
An alternative way to use Function::Parameter with Type::Tiny is to provide type
constraint expressions in parentheses:
use Types::Standard;
use Function::Parameters ':strict';
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.
AUTHOR¶
Toby Inkster <tobyink@cpan.org>.
COPYRIGHT AND LICENCE¶
This software is copyright (c) 2013-2014 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.