Question

Does anyone know of any good resources that fully explain how functions and results will fire in an Adobe AIR app where multiple things are happening at once?

As a simple test, I’ve created a single service that I just keep changing the url of, then issuing a send(). It seems that no matter how many send() calls I put in, all of these get executed before the ‘result’ eventListener function gets called for the first time.

Is this how it works? i.e. the current function gets fully executed, with the async returns queueing up to be processed after AIR has finished what it’s currently doing.

Likewise, if the user does something while all this is going on, I presume their request goes to the back of the queue as well?

All that makes sense, but I’m just wondering if it’s documented anywhere.

While I’m on one, is it recommended practice to reuse the same HTTPService in this way, or is it better to create one for each concurrent transaction? Just because it works, doesn’t mean it’s the right thing to do…

Answer 1

I’m not aware of any documentation that explains this, but I can confirm that code blocks get executed before async calls are made, or at least before their result is being processed. If it didn’t work that way, you would for instance not always be able to attach a responder to a token of a service call, because the result might already have been processed.

var token:AsyncToken = myService.someMethod();
token.addResponder(new Responder(resultHandler, faultHandler));

Developers coming from other platforms find this strange as they would expect the assignment of the responder to be too late.

So while I don’t have an official explanation about the technical details inside the Flash Player, I can assure that it works this way.

If the user does something while a call is pending, the new request will indeed just be added as a new asynchronous call. Note that we can’t realy speak of a queue, as there is no guarantee that the response of the first call comes in before the response of the second call. This depends on how much time the actual requests take.

You can perfectly reuse an HTTPService instance.

PS: Based on this, we were able to build the Operation API in Spring ActionScript. It is basically an API that allows you to execute asynchronous processes in a uniform way, without having to worry about the details of the actual async process.

The following code executes an async process and attaches a handler to it. This is also something that puzzles many developers at first, for reasons similar to the asyncToken situation.

var operation:IOperation = doSomeOperation();
operation.addCompleteListener(aCompleteHandler);
operation.addErrorListener(anErrorHandler);