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Type constraints based data validator for Perl5
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Data::Validator - Rule based validator on type constraint system


This document describes Data::Validator version 1.07.


use 5.10.0;
use Data::Validator;

# for functions
sub get {
    state $rule = Data::Validator->new(
        uri        => { isa => 'Str', xor => [qw(schema host path_query)] },

        schema     => { isa => 'Str', default => 'http' },
        host       => { isa => 'Str' },
        path_query => { isa => 'Str', default => '/' },

        method     => { isa => 'Str', default => 'GET' },

    my $args = $rule->validate(@_);
    # ...
get( uri => '' );

# for methods
sub method {
    state $rule = Data::Validator->new(
        foo => 'Str',

    my($self, $args) = $rule->validate(@_);
    # ...
Foo->method( foo => 'bar' );

# using sequenced parameters
sub seq {
    state $rule = Data::Validator->new(
        foo => 'Str',

    my $args = $rule->validate(@_);
    # ...
seq( 'bar' );          # seq() will get { foo => 'bar' }
seq({ foo => 'bar' }); # named style are NOT available!

# using Method and StrictSequenced together
sub seq_method {
    state $rule = Data::Validator->new(
        foo => 'Str',
    )->with( 'Method', 'StrictSequenced');

    my($self, $args) = $rule->validate(@_);
    # ...
Foo->seq_method( 'bar' ); # seq_method() will get { foo => 'bar' }

# using sequenced and named parameters
sub smart_seq {
    my $rule = Data::Validator->new(
        r1 => 'Str',
        r2 => 'HashRef',  # accept this
        o1 => { isa => 'Str', default => 'yes' },
        o2 => { isa => 'Num', optional => 1 },

    my $args = $rule->validate(@_);
    # ...

# all will get { r1 => 'foo', r2 => { val => 'bar' }, o1 => 'yes' }

# mixed style(recommend)
smart_seq( 'foo', { val => 'bar' }, { o1 => 'yes' } );
smart_seq( 'foo', { val => 'bar' } );

# also accept sequenced style
smart_seq( 'foo', { val => 'bar' }, 'yes' );
smart_seq( 'foo', { val => 'bar' } );

# also accept named style
smart_seq( { r1 => 'foo', r2 => { val => 'bar' }, o1 => 'yes' } );
smart_seq( { r1 => 'foo', r2 => { val => 'bar' } } );


This is yet another validation library, based on Smart::Args but less smart.

This is designed for general data validation. For example, it is useful for CSV, JSON, XML, and so on.


  • Natural as Perl code

    I love Smart::Args because it is really stylish, but it does not seem Perl-ish.

    Thus, I have designed Data::Validator in more Perl-ish way with full of Smart::Args functionality.

  • Basics on type constraint system

    Moose's type constraint system is awesome, and so is Mouse's. In fact, Mouse's type constraints are much faster than Moose's so that you need not hesitate to check types.

    Thus, I have made Data::Validator on Mouse's type constraint system.

  • Pure Perl

    Although I do not hesitate to depend on XS modules, some people think that XS modules are hard to install.

    Thus, I have written Data::Validator in pure Perl and selected dependent modules which work in pure Perl.

  • Performance

    Validators should be as fast as possible because they matter only for illegal inputs. Otherwise, one would want something like no validation option.

    This is much faster than Params::Validate, which has an XS backend, though.


Data::Validator->new( $arg_name => $rule [, ...]) :Validator

Creates a validation rule. You should cache the rules for performance.

Attributes for $rule are as follows:

  • isa => $type : Str|Object

    The type of the rule, which can be a Mouse type constraint name, a class name, or a type constraint object of either Mouse or Moose (i.e. it's duck-typed).

  • does => $role : Str|Object

    The type of the rule, which can be a Mouse type constraint name, a role name, or a type constraint object of either Mouse or Moose (i.e. it's duck-typed).

    Note that you cannot use it with the isa attribute.

  • coerce => $should_coercion : Bool

    If false, the rule does not try to coerce when the validation fails. Default to true.

  • default=> $value : Any | CodeRef

    The default value for the argument. If it is a CODE reference, it is called in scalar context as $default->($validator, $rule, $args) and its return value is used as a default value.

    Because arguments are validated in the order of definitions, default callbacks can rely on the previously-filled values:

      my $v = Data::Validator->new(
          foo => { default => 99 },
          bar => { default => sub {
              my($validator, $this_rule, $args) = @_;
              return $args->{foo} + 1;
          } },
      $v->validate();          # bar is 100
      $v->validate(foo => 42); # bar is 43

    Unlike Moose/Mouse's default, any references are allowed, but note that they are statically allocated.

  • optional => $value : Bool

    If true, users can omit the argument. Default to false.

  • xor => $exclusives : ArrayRef

    Exclusive arguments, which users cannot pass together.

  • documentation => $doc : Str

    Descriptions of the argument.

    This is not yet used anywhere.

$validator->find_rule($name :Str)

Finds the rule named $name. Provided for error handling.

$validator->with(@extensions) :Validator

Applies @extensions to $validator and returns itself.

See "EXTENSIONS" for details.

$validator->validate(@args) :HashRef

Validates @args and returns a restricted HASH reference.

Restricted hashes are hashes which do not allow to access non-existing keys, so you must check a key exists in the hash before fetching its values.


There are extensions which changes behaviours of validate().


Takes the first argument as an invocant (i.e. class or object instance), and returns it as the first value:

my($invocant, $args) = $rule->validate(@_);


Deals with arguments in mixing sequenced style and named style. The sequenced style should be passed by the order of argument rules, and the named style arguments should be the last argument as HASH ref.

The typical usage is that the required arguments as sequenced style, and some optional arguments as named style.


Deals with arguments in sequenced style, where users should pass arguments by the order of argument rules, instead of by-name.

Note that single HASH ref argument was dealt as named-style arguments, but this feature is NOT available since version 1.01.


Deals with arguments in sequenced style, where users should pass arguments by the order of argument rules, instead of by-name.

Note that if the last argument is a HASH reference, it is regarded as named-style arguments.


Regards unknown arguments as extra arguments, and returns them as a list of name-value pairs:

my($args, %extra) = $rule->validate(@_);


Does not throw errors. Instead, it provides validators with the errors attribute:

my $args = $v->validate(@_); # it never throws errors
if($v->has_errors) {
    my $errors = $v->clear_errors;
    foreach my $e(@{$errors}) {
        # $e has 'type', 'message' and 'name'
        print $e->{message}, "\n";


Does not report stack backtrace on errors, i.e. uses croak() instead of confess() to throw errors.


Does not make the argument hash restricted.


Perl 5.8.1 or later.


All complex software has bugs lurking in it, and this module is no exception. If you find a bug please either email me, or add the bug to cpan-RT.







Hash::Util for a restricted hash.


Fuji, Goro (gfx)


Copyright (c) 2010, Fuji Goro (gfx). All rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

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