NAME

MooX::Params::CompiledValidators - A Moo::Role for using Params::ValidationCompiler.

SYNOPSIS

    use Moo;
    use Types::Standard qw( Str );
    with 'MooX::Params::CompiledValidators';

    sub any_sub {
        my $self = shift;
        my $arguments = $self->validate_parameters(
            {
                $self->parameter(customer_id => $self->Required),
            },
            { @_ }
        );
        ...
    }

    # Implement a local version of the ValidationTemplates
    sub ValidationTemplates {
        return {
            customer_id => { type => Str },
        };
    }

DESCRIPTION

This role uses Params::ValidationCompiler to create parameter validators on a per method basis that can be used in the methods of your Moo or Moose projects.

The objective is to create a single set of validation criteria - ideally in a seperate role that can be used along side of this role - that can be used to consistently validate parameters throughout your application.

The validators created by Params::ValidationCompiler are cached after they are created the first time, so they will only be created once.

Validation-Templates

A validation-template is a structure (HashRef) that Params::ValidationCompiler::validation_for() uses to validate the parameter and basically contains three keys:

• type

  Params::ValidationCompiler supports a number of type systems, see their documentation.

• default

  Define a default value for this parameter, either a simple scalar or a code-ref that returns a more complex value.

• optional

  By default false, required parameters are preferred by Params::ValidationCompiler

The required ValidationTemplates() method

The objective of this module (Role) is to standardise parameter validation by defining a single set of Validation Templates for all the parameters in a project. This is why the MooX::Params::CompiledValidators role requires a ValidationTemplates method in its consuming class. The ValidationTemplates method is needed for the parameter() method that is also supplied by this role.

This could be as simple as:

    package MyTemplates;
    use Moo::Role;

    use Types::Standard qw(Str);
    sub ValidationTemplates {
        return {
            customer_id => { type => Str },
            username    => { type => Str },
        };
    }

The Required method

validation_for() uses the attribute optional so this returns 0

The Optional method

validation_for() uses the attribute optional so this returns 1

The validate_parameters() method

Returns a (locked) hashref with validated parameters or die()s trying...

Given:

    use Moo;
    with 'MooX::Params::CompiledValidators';

    sub show_user_info {
        my $self = shift;
        my $args = $self->validate_parameters(
            {
                customer_id => { type => Str, optional => 0 },
                username    => { type => Str, optional => 0 },
            },
            { @_ }
        );
        return {
            customer => $args->{customer_id},
            username => $args->{username},
        };
    }

One would call this as:

    my $user_info = $instance->show_user_info(
        customer_id => 'Blah42',
        username    => 'blah42',
    );

Parameters

Positional:

1. $validation_templates

   A hashref with the parameter-names as keys and the "Validation-Templates" as values.

2. $values

   A hashref with the actual parameter-name/value pairs that need to be validated.

Responses

• Success (scalar context, recommended)

  A locked hashref.

• Success (list context, only if you need to manipulate the result)

  A list that can be coerced into a hash.

• Error

  Anything Params::ValidationCompiler will throw for invalid values.

The validate_positional_parameters() method

Like $instance->validate_parameters(), but now the pairs of name, validation-template are passed in an arrayref, that is split into lists of the names and templates. The parameters passed -as an array- will be validated against the templates-list, and the validated results are combined back into a hash with name/value pairs. This makes the programming interface almost the same for both named-parameters and positional-parameters.

Returns a (locked) hashref with validated parameters or die()s trying...

Given:

    use Moo;
    with 'MooX::Params::CompiledValidators';

    sub show_user_info {
        my $self = shift;
        my $args = $self->validate_positional_parameters(
            [
                customer_id => { type => Str, optional => 0 },
                username    => { type => Str, optional => 0 },
            ],
            \@_
        );
        return {
            customer => $args->{customer_id},
            username => $args->{username},
        };
    }

One would call this as:

    my $user_info = $instance->show_user_info('Blah42', 'blah42');

Parameters

Positional:

1. $validation_templates

   A arrayref with pairs of parameter-names and "validation templates".

2. $values

   A arrayref with the actual values that need to be validated.

Responses

• Success (list context)

  A list that can be coerced into a hash.

• Success (scalar context)

  A locked hashref.

• Error

  Anything Params::ValidationCompiler will throw for invalid values.

The parameter() method

Returns a parameter_name, validation_template pair that can be used in the parameters argument hashref for Params::ValidationCompiler::validadion_for()

Parameters

Positional:

1. $name (Required)

   The name of this parameter (it must be a kind of identifier: m{^\w+$})

2. $required (Optional)

   One of $class->Required or $class->Optional but will default to $class->Required.

3. $extra (Optional)

   This optional HashRef can contain the fields supported by the params parameter of validation_for(), even overriding the ones set by the $class->ValidationTemplates() for this $name - although optional is set by the previous parameter in this sub.

   This parameter is mostly used for the extra feature to pass a lexically scoped variable via store.

Responses

• Success

  A list of $parameter_name and $validation_template.

    (this_parm => { optional => 0, type => Str, store => \my $this_param })

NOTE on "Unknown" parameters

Whenever $self->parameter() is called with a parameter-name that doesn't resolve to a template in the ValidationTemplates() hash, a default "empty" template is produced. This will mean that there will be no validation on that value, although one could pass one as the third parameter:

    use Moo;
    use Types::Standard qw( StrMatch );
    with qw(
        MyTemplates
        MooX::Params::CompiledValidators
    );

    sub show_user_info {
        my $self = shift;
        my $args = $self->validate_parameters(
            {
                $self->parameter(customer_id => $self->Required),
                $self->parameter(
                    email => $self->Required,
                    { type => StrMatch[ qr{^ [-.\w]+ @ [-.\w]+ $}x ] },
                ),
            },
            {@_}
        );
        return {
            customer => $args->{customer_id},
            email    => $args->{email},
        };
    }

The extra store attribute

Both validate_parameters() and validate_positional_parameters support the extra store attribute in a validation template that should be a scalar-reference where we store the value after successful validation.

One can pick and mix with validation templates:

    use Moo;
    use Types::Standard qw( StrMatch );
    with qw(
        MyTemplates
        MooX::Params::CompiledValidators
    );

    sub show_user_info {
        my $self = shift;
        $self->validate_parameters(
            {
                $self->parameter(customer_id => $self->Required, {store => \my $customer_id),
                email => {
                    type     => StrMatch[ qr{^ [-.\w]+ @ [-.\w]+ $}x ],
                    optional => 0,
                    store    => \my $email
                },
            },
            { @_ }
        );
        return {
            customer => $customer_id,
            email    => $email,
        };
    }

One would call this as:

    my $user_info = $instance->show_user_info(
        customer_id => 'Blah42',
        email       => 'blah42@some.tld',
    );

One could argue that using (lexical) variables -instead of addressing keys of a locked hash- triggers the error caused by a typo at compile-time rather than at run-time.

NOTE: In order to keep the scope of the variable, where the value is stored, limited, the store attribute should only be used from the per method override option extra for $self->parameter().

AUTHOR

© MMXXI - Abe Timmerman abeltje@cpan.org

LICENSE

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

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.