---
name: "Attribute::Params::Validate"
section: "3pm"
platform: "linux"
package: "libparams-validate-perl"
version: "1.13-1+b1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/Attribute::Params::Validate"
---

# Attribute::Params::Validate(3pm)

Define validation through subroutine attributes

## NAME

Attribute::Params::Validate - Define validation through subroutine attributes

## VERSION

version 1.13

## SYNOPSIS

```
  use Attribute::Params::Validate qw(:all);
  # takes named params (hash or hashref)
  # foo is mandatory, bar is optional
  sub foo : Validate( foo => 1, bar => 0 )
  {
      ...
  }
  # takes positional params
  # first two are mandatory, third is optional
  sub bar : ValidatePos( 1, 1, 0 )
  {
      ...
  }
  # for some reason Perl insists that the entire attribute be on one line
  sub foo2 : Validate( foo => { type => ARRAYREF }, bar => { can => [ 'print', 'flush', 'frobnicate' ] }, baz => { type => SCALAR, callbacks => { 'numbers only' => sub { shift() =~ /^\d+$/ }, 'less than 90' => sub { shift() < 90 } } } )
  {
      ...
  }
  # note that this is marked as a method.  This is very important!
  sub baz : Validate( foo => { type => ARRAYREF }, bar => { isa => 'Frobnicator' } ) method
  {
      ...
  }
```

## DESCRIPTION

The Attribute::Params::Validate module allows you to validate method or function call parameters just like Params::Validate does.  However, this module allows you to specify your validation spec as an attribute, rather than by calling the `"validate"` routine.

Please see Params::Validate for more information on how you can specify what validation is performed.

### EXPORT

This module exports everything that Params::Validate does except for the `"validate"` and `"validate_pos"` subroutines.

### ATTRIBUTES

- •

  Validate

  This attribute corresponds to the `"validate"` subroutine in Params::Validate.

- •

  ValidatePos

  This attribute corresponds to the `"validate_pos"` subroutine in Params::Validate.

### OO

If you are using this module to mark **methods** for validation, as opposed to subroutines, it is crucial that you mark these methods with the `":method"` attribute, as well as the `"Validate"` or `"ValidatePos"` attribute.

If you do not do this, then the object or class used in the method call will be passed to the validation routines, which is probably not what you want.

### CAVEATS

You **must** put all the arguments to the `"Validate"` or `"ValidatePos"` attribute on a single line, or Perl will complain.

## SEE ALSO

Params::Validate

## AUTHORS

- •

  Dave Rolsky \<autarch@urth.org\>

- •

  Ilya Martynov \<ilya@martynov.org\>

## COPYRIGHT AND LICENSE

This software is Copyright (c) 2014 by Dave Rolsky and Ilya Martynov.

This is free software, licensed under:

```
  The Artistic License 2.0 (GPL Compatible)
```