calm in the chaos

Firstly, Happy New Year! Hope your ‘09 is off to a flyer!

Secondly, sorry about the rather mundane heading - couldn’t really think of what to call this post. I’ve been typing all sorts of things into Google trying to find a solution to what I’ll describe below.

I’m continuing the project I started in early December and having some very interesting battles with AS3 and the Flex framework. I’d like to document one of those battles today.

What I wanted to do was send parameters along with an event so that the event listener had access to them. Now I’m fully aware of how to do that when I’m in charge of dispatching the event, but was (and still am) at a loss as to how to add them in the following instance:

myComboBox.addEventListener(Event.CHANGE, eventListener);

This call to addEventListener occurs where the variables I want to pass get defined.

Here’s the code that I attempted to use (without luck) to get the parameters passed along with the event:

myComboBox.addEventListener(PodEvent.CHANGE, eventListener);
var myEvent:PodEvent = new PodEvent(PodEvent.CHANGE);
myEvent.displayTriggerValue = displayTriggerValue;
myEvent.formItem = triggerDisplay;
myComboBox.dispatchEvent(myEvent);

I could get the displayTriggerListener to run when the combobox changed, but the variables that I added to myEvent wouldn’t make it in there (further to that I was having type coercion difficulties, but that’s another story I think). The initial dispatchEvent was also allowing the eventListener to get the parameters, but obviously the idea is to have them passed along with every PodEvent.CHANGE event.

Now initially I got around this using closures (a new term to me). I understand the issues of using anonymous functions (ie. garbage collection issues) so searched some more for answers. I found nada.

So after a nights rest and a few more hours wrestling with it today, I’ve come up with the following solution that I’m rather chuffed about. I use a Dictionary to store a reference to the component and in turn create an object associated with that Dictionary element to store the parameters I want to pass into the eventListener function. Perhaps some code will illustrate what the hell I just typed (for me and you both ;-)

myParamDictionary[myComboBox] = {param1: value1, param2: value2};

The myParamDictionary is a private var in the class so is accessible within the eventListener

private function eventListener(e:Event):void {
	var _local:* = myParamDictionary[e.target]
	// rest of the implementation here. You can access the previously set parameters by _local.param1, _local.param2...
}

And to my utter delight (and surprise) it works!

The only downside is there’s no type checking on the parameters, which is what I originally wanted to use a custom event for.

If you’ve got a suggestion for my initial problem or a critique for my end solution please don’t be shy and post them!

I’m having a few issues with Flex Builder and Sephiroth’s FlashTracer Firefox extension at the moment. The first issue is that the Design view in Flex actually traces things like:

-> Begin call to AS: getGlobalPoint(Canvas1,-1,-1)
<- End call to AS: getGlobalPoint, Result = 494,409
-> Begin call to AS: showConstraints(false)
<- End call to AS: showConstraints, Result = null
-> Begin call to AS: getGlobalPoint(Canvas1,-1,-1)

Which can clutter up the FlashTracer console. Not only that, it also causes the FlashTracer to choke on the number of lines it is displaying which in turn causes Firefox to crash. Not an ideal way to debug an application.

I set out to remedy my problem this morning. And I managed to stumble across a Java version offering the same functionality as FlashTracer. Flash Tracer (imaginatively named ;-) can be found at it’s Google Code home. As I’m running the Firefox extension in it’s own window, this fits well with my work flow at the moment. So the fact that it’s not integrated into Firefox doesn’t matter for me so much.

Does anyone have any tips for getting Flex Builder to stop its incessant chitter chatter of trace outputs?

Still related to the flashlog.txt file, I’m completely baffled as to why running an Air application locks the log file and stops any other process from writing to it. So when debugging, be sure to close down all your Air apps. Very handy, certainly aids with my workflow when I’m trying to create things in Flash. Thanks Adobe. And I’ve logged a wishlist request and asked a few questions using the usual channels so will hopefully receive a good reason for the file being locked (I’m assuming it’s not just for kicks).

I just realised that the latest version of the Firefox plugin is only 2.2.0 yet on Sephiroth’s page there’s a 2.3.1 version. I’ll install that and see if it resolves the crashing issues).

UPDATE: I just came across SOS Max via Wezside’s blog Ahhh, you’ve gotta love Google! The SOS Max debugger looks very good and I think it probably trumps both FlashTracer and Flash Tracer.

MVC is on my mind at the moment. I’ve read more about this and other design patterns and frameworks in the last few weeks than I care to recount (though I do hope it’s starting to sink in).

This is all in preparation for the biggest project I’ve ever tackled.

Now unlike other projects, I’ve stopped myself from just delving in and getting amongst the code.

I’m not sure I like this new approach though. It’s making me feel very stressed after not really having made a “proper” (read: there’s not much code sitting in classes) start on something I thought was going to be a lot easier than it’s turning out to be.

However, during my research (and after a few hands in head moments) I came across a great article that talks about MVC - Removing The Model-View-Controller Straitjacket In particular it discusses the difficulty in defining something which can mean many things to many people in many situations. Malcolm Tredinnick suggests to, “stop saying ‘thing X is (or is not) MVC’. You’re almost certainly fudging at the edges and certainly not making things any clearer.”

He also links to an original document from 1979 that sets out what MVC is. It’s pretty cool to think that the geeks back then were solving the same thing the geeks of today are.

In his summary he also offers some sage advice - “Solve problems and understand solutions in context. Don’t pigeon-hole.” I find that the problem with that advice is until you’ve tried to fit the pidgeons into their holes a few times (which seasoned OOP advocates have), it’s kinda nice to think (possibly foolishly) that they might just fit.

This is pretty much where I’m at at the moment - trying to squeeze whopping great big birds into comparably small holes. Fortunately I’ve got a big rubber MVC-Mallet to bang them in with! And some reassuring words that you shouldn’t feel too worried if things can’t be categorised exactly.

I’ll post more about what I’m doing in the coming weeks, but wanted to mention that I’m using the Mate framework (pronounced Mah-teh). It seems to offer some pretty cool features and some great help and examples on the website. There’s a few caveats with using it though. One of which (and this seems to be a bit of a recurring theme with these types of frameworks) is that certain parts of the application aren’t eligible for compile time type checking. I stumbled upon this today, and was quick to realise where the problem lay - but I’m only a few 100 lines of code in at the moment. I’ll post back when I’ve hit 10,000 lines of code and let you know if I’m still mate’s with Mate.

(I also just found this great article on similar subject matter over at as3dp.com - No Time for OOP and Design Patterns. Check it out, it’s a ripper!)

A few years back I worked on a project that used the Google Maps API and at the time I was charged with recommending to the client whether to use Flash or Javascript/HTML to get the job done. At the time there was no readily accessible Flash API for Google maps, and I wasn’t that keen to go with the Yahoo or Microsoft offerings (though Yahoo now has a very robust Flash API, the Microsoft (surprise surprise) one doesn’t… though I found this Silverlight version). FYI the Kaurna Place Names site was developed to identify and map places with Kaurna (Aboriginal) names and to encourage the use and increase knowledge of these names. It begins with names in southern Kaurna country (which is the region of Australia where I’m from).

So there’s the back story. I recently came across a post which talked about the Google Maps API now being available for Flash AS3. With my current push to learn about Flex I was also pleased to see that there were components available that you could just drop into your MXML and whamo, insta-map!

Here’s what I pieced together, hopefully it illustrates what can be done with a few Flex components and the Maps code provided from the Google Maps developer site.

View source is enabled in the following example.

Obviously it’s not a scratch on Paul Neave’s venerable Flash Earth, but then this example only took 15 minutes to knock together ;-)