On Sun, Apr 13, 2008 at 10:50 AM, Doug McCune <doug@...> wrote:
> we'll be pushing out more examples, especially of how to use the
> EventGenerator since that's something I think a lot of people have
> needed to do.

Yeah, on has to go over the code a bit to see how it works, but that
EventGenerator is pretty flexible and easy to use once you understand
how the UMEvents, on which it relies, work.

UMEvents are CairngormEvent subclasses that have this callbacks:Callbacks
property. Callbacks are just a couple of functions packed together (under an
agreed interface (mx.rpc.IResponder)) that the command, which was triggered by
the event, can *call back* when it's done (or if it has failed)... letting
know however actually was behind that callback object what happened. (From
the flexcoders.com interview it seems that these were built to be able to let
know the view that dispatched the event the result of the call without having
to clutter the model with unnecesary data that was only going to be used to
let that original view know what had happened anyways.)

When you define and EventGenerator, you set the list of events you want to be
dipatched. when you fire it off, the EventGenerator will take the first one,
will set it's callbacks properties so that it (the EG) will know when the
command is done, and the will dispatch it. If the EG is set to run in
sequence, it will then wait for the command associated with the event to run
the callback that lets it know that it can then run the next command; It'll
then run it, and so on until it runs out of events.

One can find, in a comment that doesn't show on the asdocs, the AS example
provided by the author (there's another that uses mxml notation and
preinstantiated events):

<quote><code>
// If any task/event fails, then abort the task processing entirely
(e.g. trigger == "0")
var parallelEvents :Array = [LoadUserProfileEvent,LoadMetaDataEvent];
var parallelGen :EventGenerator = new
EventGenerator(parallelEvents,null,0,"parallel");

// Now, manually add the parallel generator into the list for the
consecutive generator...
var consecutiveTasks : Array = [LoadBundleEvent,
parallelGen, LoadUserPreferencesEvent];

var handlers : CallBacks = new
Callbacks(whenAppIsReady, notifyUserOfError);
var cmd : EventGenerator = new
EventGenerator(consecutiveTasks,handlers,0);
cmd.dispatch();
</code></quote>

For this to work, you have to make sure that, from the command that might be
run from an event generated by this EventGenerator, once it is done, you call
the appropriate callback on the event or else the EventGenerator will just sit
there waiting forever. You can do something along these lines:

if (_yourTypedUMEvent.callbacks) _yourTypedUMEvent.callbacks.result(null);
// or _yourTypedUMEvent.callbacks.fault(info); // if something went wrong.

Please note that it seems that this was designed with asynchronous commands in
mind only; if you run a command that can send a result right away, you might
get a racing condition bug which will produce a runtime error.

EventGenerator will take UMEvent classes, instance or other EventGenerators,
so you can nest them in arbitrarily interesting ways. Pretty cool.

--
gabriel montagné láscaris comneno
http://rojored.com
t/506.8392.2040