# NAME

Catalyst::TraitFor::Request::ContentNegotiationHelpers - assistance with content negotiation

# SYNOPSIS

For [Catalyst](https://metacpan.org/pod/Catalyst) v5.90090+

    package MyApp;

    use Catalyst;

    MyApp->request_class_traits(['Catalyst::TraitFor::Request::ContentNegotiationHelpers']);
    MyApp->setup;

For [Catalyst](https://metacpan.org/pod/Catalyst) older than v5.90090

    package MyApp;

    use Catalyst;
    use CatalystX::RoleApplicator;

    MyApp->apply_request_class_roles('Catalyst::TraitFor::Request::ContentNegotiationHelpers');
    MyApp->setup;

In a controller:

    package MyApp::Controller::Example;

    use Moose;
    use MooseX::MethodAttributes;

    sub myaction :Local {
      my ($self, $c) = @_;
      my $best_media_type = $c->req->choose_media_type('application/json', 'text/html');
    }

    sub choose :Local {
      my ($self, $c) = @_;
      my $body = $c->req->on_best_media_type(
        'no_match' => sub { 'none' },
        'text/html' => sub { 'html' },
        'application/json' => sub { 'json' });

      $c->res->body($body);
    }

# DESCRIPTION

When using [Catalyst](https://metacpan.org/pod/Catalyst) and developing web APIs it can be desirable to examine
the state of HTTP Headers of the request to make decisions about what to do,
for example what format to return (HTML, XML, JSON, other).  This role can
be applied to your [Catalyst::Request](https://metacpan.org/pod/Catalyst::Request) to add some useful helper methods for
the more common types of server side content negotiation.

Most of the real work is done by [HTTP::Headers::ActionPack::ContentNegotiation](https://metacpan.org/pod/HTTP::Headers::ActionPack::ContentNegotiation),
this role just seeks to make it easier to use those features.

# ATTRIBUTES

This role defines the following attributes.

## content\_negotiator

This is a 'bare' attribute with no direct accessors.  It expose a few methods to
assist in content negotation.

# METHODS

This role defines the following methods:

## choose\_media\_type (@array\_of\_types)

Given an array of possible media types ('application/json', 'text/html', etc.)
return the one that is the best match for the current request (by looking at the
current request ACCEPT header, parsing it and comparing).

## accepts\_media\_type ($type)

Given a string type that is a media type (text/html, application/json) returns true
if that type is acceptable to the requesting client.

## on\_best\_media\_type (%callbacks)

Given a hash where the keys are media types and the values are coderefs, execute
and return the value of the coderef whose key is the best match for that media type
(based on the result of ["choose\_media\_type"](#choose_media_type).  For example:

    my $body = $c->req->on_best_media_type(
      'no_match' => sub { 'none' },
      'text/html' => sub { 'html' },
      'application/json' => sub { 'json' });

    $c->res->body($body);

The coderef will receive the current request object as its single argument.

If there are no matches, execute the coderef associated with a 'no\_match' key
or return undef if no such key exists.

## choose\_language (@array\_of\_langauges)

Given an array of possible media types ('en-US', 'es', etc.)
return the one that is the best match for the current request.

## accepts\_language ($type)

Given a string type that is a language string returns true
if that is acceptable to the requesting client.

## on\_best\_language (%callbacks)

Works like ["on\_best\_media\_type"](#on_best_media_type) but matches language.

## choose\_charset (@array\_of\_character\_sets)

Given an array of possible media types ("UTF-8", "US-ASCII", etc.)
return the one that is the best match for the current request.

## accepts\_charset ($type)

Given a string type that is a charset string returns true
if that is acceptable to the requesting client.

## on\_best\_charset (%callbacks)

Works like ["on\_best\_media\_type"](#on_best_media_type) but matches charset.

## choose\_encoding (@array\_of\_encodings)

Given an array of possible encodings ("gzip", "identity", etc.)
return the one that is the best match for the current request.

## accepts\_encoding ($type)

Given a string type that is an encoding string returns true
if that is acceptable to the requesting client.

## on\_best\_encoding (%callbacks)

Works like ["on\_best\_media\_type"](#on_best_media_type) but matches encoding.

## raw\_choose\_media\_type

## raw\_choose\_language

## raw\_choose\_charset

## raw\_choose\_encoding

These are methods that map directly to the underlying [HTTP::Headers::ActionPack::ContentNegotiation](https://metacpan.org/pod/HTTP::Headers::ActionPack::ContentNegotiation)
object.  The are basicallty the same functionality except they require two arguments
(an additional one to support the HTTP header string).  You generally won't need them unless
you need to compare am HTTP header that is not one that is part of the current request.

# AUTHOR

John Napiorkowski [email:jjnapiork@cpan.org](email:jjnapiork@cpan.org)

# SEE ALSO

[Catalyst](https://metacpan.org/pod/Catalyst), [Catalyst::Request](https://metacpan.org/pod/Catalyst::Request), [HTTP::Headers::ActionPack::ContentNegotiation](https://metacpan.org/pod/HTTP::Headers::ActionPack::ContentNegotiation)

# COPYRIGHT & LICENSE

Copyright 2015, John Napiorkowski [email:jjnapiork@cpan.org](email:jjnapiork@cpan.org)

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