NAME

Catalyst::Plugin::Snippets - Make sharing data with clients easy

SYNOPSIS

    package MyApp;

    # use this plugin, and any Cache plugin
        use Catalyst qw/
        Cache::FastMmap
        Snippets
    /;

    package MyApp::Controller::Foo;

    sub action : Local {
        my ( $self, $c ) = @_;
        # ...
        $c->snippet( $namespace, $key, $value );
    }

    sub foo : Local {
        my ( $self, $c ) = @_;
        $c->serve_snippet( $namespace, \%options ); # namespace defaults to $c->action->name;
    }

    sub other_action : Private {
        my ( $self, $c ) = @_;
        my $value = $c->snippet( $namespace, $key );
    }

DESCRIPTION

This plugin provides a means of setting data that can then be queried by a client in a different request.

This is useful for making things such as progress meters and statistics amongst other things.

This plugin provides an API for storing data, and a way to conveniently fetch it too.

METHODS

snippet $namespace, $key, [ $value ]

This is an accessor for the client exposed data.

If given a value it will set the value, and otherwise it will retrieve it.

serve_snippet [ $namespace, ] [ %options ]

This method will serve data bits to the client based on a key. The namespace defaults to the action name.

The optional options array reference will take this values. This array will take it's default first from $c->config->{"snippets:$namespace"} and then it will revert to $c->config->{snippets}.

See the "CONFIGURATION" section for detailed options.

serialize_snippet $value, \%options

This method is automatically called by serve_snippet to serialize the value in question.

send_snippet $value, \%options

This method is automatically called by serve_snippet to set the response body.

INTERNAL METHODS

setup

Set up configuration defaults, etc.

CONFIGURATION

format

This takes either json, plain (the default) or a code reference.

The json format specifies that all values values will be serialized as a JSON expression suitable for consumption by javascript. This is reccomended for deep structures.

You can also use a code reference to implement your own serializer. This code reference should return two values: the content type, and a a value to set $c->response->body to

allow_refs

If this is disabled reference values will raise an error instead of being returned to the client.

This is true by default.

use_session_id

This fields allows you to automatically create a different "namespace" for each user, when used in conjunction with Catalyst::Plugin::Session.

This is false by default.

content_type

When the formatter type is plain you may use this field to specify the content-type header to use.

This option defaults to text/plain.

json_content_type

Since no one seems to agree on what the "right" content type for JSON data is, we have this option too ;-).

This option defaults to application/javascript+json

PRIVACY CONCERNS

Like session keys, if the values are private the key used by your code should be sufficiently hard to guess to protect the privacy of your users.

Please use the use_session_id option for the appropriate namespace unless you have a good reason not to.

RECIPES

Ajax Progress Meter

Suppuse your app runs a long running process in the server.

    sub do_it {
        my ( $self, $c ) = @_;

        IPC::Run::run(\@cmd);

        # done
    }

The user might be upset that this takes a long while. If you can track progress, along these lines:

    my $progress = 0;

    IPC::Run::run(\@cmd, ">", sub {
        my $output = shift;
        $progress++ if ( $output =~ /made_progress/ );
    });

then you can make use of this data to report progress to the user:

    $c->snippet( progress => $task_id => ++$progress )
        if ( $output =~ /made_progress/  );

Meanwhile, javascript code with timers could periodically poll the server using an ajax request to update the progress level. To expose this data to the client create an action somewhere:

    sub progress : Local {
        my ( $self, $c ) = @_;
        $c->serve_snippet;
    }

and have the client query for "/controller/progress/$task_id".