trusty (3) Jifty::Continuation.3pm.gz

NAME

       Jifty::Continuation - Allows for basic continuation-based programming

DESCRIPTION

       In programming, a continuation is a construct that allows you to freeze the current state of a program
       and then recover that state later by calling the continuation. For example, you could save a continuation
       when throwing an exception to save the state, an exception handler could resolve the problem that caused
       the exception, and then call the continuation to resume execution at the point where the exception was
       thrown now that the problem has been solved.

       In Jifty, continuations are used to save the state of a request (and sometimes the response).
       Continuations can be used in situations such as these:

       1.  A user visits a page that requires login to view. The dispatcher saves a continuation and then sends
           the user off to the login page. Once the user logs in successfully, the login action can call the
           continuation to return the user back to the original page.

       2.  A blogging application might have a "Edit" link on each post to allow the editor to jump to the
           change page. If this link includes a saved continuation, then the "Save" button could trigger that
           continuation to be called to return the user back to the original page where they clicked "Edit".
           This way, it could return the user to the view page, or a list page, or an administrative view
           depending on which page the user started the edit process from.

       3.  If you have a wizard for editing some information in your application, but entering some data may
           require jumping to another page you can save a continuation to allow the user to return after
           editing. If that page also requires a jump to yet another page, you can save another continuation.
           Since continuations save a stack of previous continuations, you can return twice to get back to the
           wizard.

       "Jifty::Continuation" handles the details of saving this information for later recovery. When a
       continuation is saved, the current request and response are saved to the database in the current user's
       session. When a continuation is called, the current request and response become those that were saved in
       the continuation. A continuation can be called at any point in the same session.

       Continuations store a Jifty::Request object and the Jifty::Response object for the request.  They can
       also store arbitrary code to be run when the continuation is called.

       Continuations can also be arbitrarily nested.  This means that returning from one continuation will drop
       you into the continuation that is one higher in the stack.

       Continuations are generally created just before their request would take effect, activated by the
       presence of certain query parameters.  The rest of the request is saved, its execution is to be continued
       at a later time.

       Continuations are run after any actions have run.  When a continuation is run, it restores the request
       that it has saved away into it, and pulls into that request the values any return values that were
       specified when it was created.  The continuations code block, if any, is then called, and then the
       filled-in request is then passed to the Jifty::Dispatcher.

   new PARAMHASH
       Saves a continuation at the current state.  Possible arguments in the "PARAMHASH":

       parent
           A Jifty::Continuation object, or the "id" of one.  This represents the continuation that this
           continuation should return to when it is called.  Defaults to the current continuation of the current
           Jifty::Request.

       request
           The Jifty::Request object to save away.  Defaults to an empty Jifty::Request object.

       response
           The Jifty::Response object that will be loaded up when the continuation is run.  Most of the time,
           the response isn't stored in the continuation, since the continuation was saved away before the
           actions got run.  In the case when continuations are used to preserve state across a redirect,
           however, we tuck the Jifty::Response value of the previous request into the continuation as well.
           Defaults to an empty Jifty::Response object.

       code
           An optional subroutine reference to evaluate when the continuation is called.

   return_path_matches
       Returns true if the continuation matches the current request's path, and it would return to its caller in
       this context.  This can be used to ask "are we about to call a continuation?"

   call
       Call the continuation; this is generally done during request processing, after actions have been run.
       Jifty::Request::Mapper-controlled values are filled into the stored request based on the current request
       and response.  During the process, another continuation is created, with the filled-in results of the
       current actions included, and the browser is redirected to the proper path, with that continuation.

   return
       Returns from the continuation by pulling out the stored request, and setting that to be the active
       request.  This shouldn't need to be called by hand -- use "return_from_continuation" in Jifty::Request,
       which ensures that all requirements are met before it calls this.

   delete
       Remove the continuation, and any continuations that would return to its scope, from the session.

SEE ALSO

       Jifty::Manual::Continuations

LICENSE

       Jifty is Copyright 2005-2010 Best Practical Solutions, LLC.  Jifty is distributed under the same terms as
       Perl itself.