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Catalyst::Plugin::StatusMessage(3) User Contributed Perl Documentation Catalyst::Plugin::StatusMessage(3)

Catalyst::Plugin::StatusMessage - Handle passing of status (success and error) messages between screens of a web application.


    use Catalyst qr/

In controller where you want to save a message for display on the next page (here, once the "delete" action taken is complete, we are redirecting to a "list" page to show the status [we don't want to leave the delete action in the browser URL]):

        {mid => $c->set_status_msg("Deleted widget")}));

Or, to save an error message:

        {mid => $c->set_error_msg("Error deleting widget")}));

Then, in the controller action that corresponds to the redirect above:

    sub list :Path {
        my ($self, $c) = @_;

And, to display the output (here using Template Toolkit):

    <span class="message">[% status_msg %]</span>
    <span class="error">[% error_msg %]</span>

There are a number of ways people commonly use to pass "status messages" between screens in a web application.
  • Using $c->stash: The stash only exists for a single request, so this approach can leave the wrong URL in the user's browser.
  • Using $c->flash: The "flash" feature does provide a mechanism where the application can redirect to an appropriate URL, but it can also lead to a race condition where the wrong status message is displayed in the wrong browser window or tab (and can therefore be confusing to the users of your application).
  • Query parameters in the URL: This suffers from issues related to long/ugly URLs and leaves the message displayed even after a browser refresh.

This plugin attempts to address these issues through the following mechanisms:

  • Stores messages in the "$c->session" so that the application is free to redirect to the appropriate URL after an action is taken.
  • Associates a random 8-digit "token" with each message, so it's completely unambiguous what message should be shown in each window/tab.
  • Only requires that the token (not the full message) be included in the redirect URL.
  • Automatically removes the message after the first time it is displayed. That way, if users hit refresh in their browsers they only see the messages the first time.

Load both messages that match the token parameter on the URL (e.g., into the stash for display by the viewer.

In general, you will want to include this in an "auto" or "base" (if using Chained dispatch) controller action. Then, if you have a "template wrapper page" that displays both ""status_msg"" and ""error_msg"", you can automatically and safely send status messages to any related controller action.

The location inside $c->session where messages will be stored. Defaults to ""status_msg"".

The name of the URL param that holds the token on the page where you want to retrieve/display the status message. Defaults to ""mid"".

The name of the stash key where "success" status messages are loaded when "$c->load_status_msgs" is called. Defaults to "status_msg".

The name of the stash key where error messages are loaded when "$c->load_status_msgs" is called. Defaults to "error_msg".

Here is a quick example showing how Catalyst::Plugin::StatusMessage can be configured in

    # Configure Catalyst::Plugin::StatusMessage
        'Plugin::StatusMessage' => {
            session_prefix          => 'my_status_msg',
            token_param             => 'my_mid',
            status_msg_stash_key    => 'my_status_msg',
            error_msg_stash_key     => 'my_error_msg',

Note: You normally shouldn't need any of the information in this section to use Catalyst::Plugin::StatusMessage.

A dynamically generated accessor to retrieve saved error messages

A dynamically generated accessor to retrieve saved status messages

A dynamically generated accessor to save error messages

A dynamically generated accessor to save status messages

Subref that handles default values and lets them be overriden from the MyApp configuration.

Fetch the requested message type from the user's session

Save a message to the user's session

Load both messages that match the token param (mid=###) into the stash for display by the view.

Called at startup to install getters and setters for each type of message (status & error)

Kennedy Clark,

With many thanks to Matt Trout (MST) for coaching on the details of Catalyst Plugins and for most of the magic behind the current implementation.

This library is free software. You can redistribute it and/or modify it under the same terms as Perl itself.
2012-05-16 perl v5.32.1

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