If you want to let something only happen if the event wasn’t canceled it should [...]]]> When you dispatch events I bet that most Flash/Flex devs don’t take advantage of the fact that dispatchEvent returns a Boolean value indicating wether or not the event has been canceled. Normally your code looks similar to this:

var event:MyEvent = new MyEvent(MyEvent.FOO);
dispatchEvent(event)

If you want to let something only happen if the event wasn’t canceled it should look like this:

// The second "true" sets the event cancelable, first one sets bubbles
var event:MyEvent = new MyEvent(MyEvent.FOO, true, true);
if(dispatchEvent(event)){
   // do the actual task
}

With the code above the event listener can control if the actual task gets executed or not:

dispatchingInstance.addEventListener(MyEvent.FOO, fooHandler);
function fooHandler(event:MyEvent):void{
   // depending on what you want to achieve you can cancel the event by calling preventDefault
   event.preventDefault();
   // this will cause dispatchEvent to return false so the actual task doesn't get executed
}

A real life usecase for UI related events could be dispatching an event before closing a popup window:

function closeButtonHandler(event:Event):void{
   if(dispatchEvent(new MyWindowEvent(MyWindowEvent.CLOSE, true, true)){
      PopUpManager.closePopup(this);
   }
}

Cancelable events are also very interesting when you develop APIs because it offers powerful and easy to use hooks for the API user.
I am making heavy use of cancelable events in my swizdesktop lib. Catching the different update phase events you get hooks to stop the update process by calling preventDefault on the listened event.

More or less I have [...]]]> A while back I worked on an AIR client which had to be capable uploading very large files. In this scenario you have to upload files in little chunks. The research on how to solve this took me quite a while so I thought it would make sense to post my findings.

More or less I have taken the NirvanixBinaryUploader as a base and then extended (I should say forked) it to fit my needs.

The class UploadFile takes a file and upload URL as constructor arguments. You can also define a separate resumeUrl if it differs from the upload URL. Further you can set the flag doCalcMD5 to true which is kind of experimental. It works using the as3corelib MD5Stream class but calculating the MD5 hash for large chunks like 1MB took about 20-30 secs on my machine.

I have also implement getters for bytesLoaded and bytesTotal so I can use an instance as a data source for the Flex ProgressBar in polled mode which comes in very handy.

<mx:ProgressBar source="{uploadFile}" mode="polled" label="Uploading" />

If you want to use my code I guess you want to subclass my class because it contains example code and you probably want to override at least the createBody method. However, if you have a similar scenario like me, the code might be a good start.

Another interesting read on this topic was A long journey through chunked transfer and file uploading.

Here now the code:

This is still basic functionality but since it’s open source someone may fork and extend it. [...]]]> I have build a little Twitter AS3 library which handles Twitter OAuth authentication and let’s you update your Twitter status. The lib basically uses the OAuth AS3 lib and should be a good example how to use the actual OAuth lib.

This is still basic functionality but since it’s open source someone may fork and extend it. To get a simple idea of the current feature-set have a look at the ITwitter interface.

Further I have build a simple Flex 4 example AIR app which shows things in action. The only thing you need to do upfront is registering a Twitter app to obtain an OAuth consumer key and secret which you have to add to the example:

BTW: You maybe have already granted access to your Twitter account for some apps which you can check here.

Source and Download

Usage

Add FGATracker to your BeanLoader:

Dispatch TrackPageEvent or TrackActionEvent:

From a view class (set bubbles=true):

Today I am happy to announce that the public beta of FlairLoc is available.

Features

I have build a little AIR client as an example application. Check my YouTubeAS3 project on github for the source code. The example of course uses the Swiz framework.

The meat [...]]]> Today YouTube finally released an ActionScript 3 API. Maybe this was accelerated by the move of Vimeo because they came up with an AS3 API last week.

I have build a little AIR client as an example application. Check my YouTubeAS3 project on github for the source code. The example of course uses the Swiz framework.

The meat is the Player class and the IPlayer interface which wraps the YouTube proxy object. The Player extends UIComponent and implements IVisualElement so it works decent with Flex 4. The original SWFProxy object extends Sprite which is fine for Flash but not for Flex.

If you are to lazy to study the API docs like me this screenshot might help:

Uploaded with plasq‘s Skitch!

The example is still pretty small but I’ll try to extend it when I find some time in the future.

However I disliked that I have to dispatch custom events to make getters bindable. This would normally look like this in an interface:

The problem with it is [...]]]> Lately I have started to use the presentation model approach and I like it a lot. Swiz fellow Ben Clinkinbeard has a wonderful example posted on his blog.

However I disliked that I have to dispatch custom events to make getters bindable. This would normally look like this in an interface:

[Bindable(event="customDataChanged")]
function get someData():Array;

The problem with it is that I have to dispatch an event typed “customDataChanged” from the presentation model implementation when I want the binding to be updated.
So my implementation would look like this:

private var _someData:Array;
public function get someData():Array{
    return _someData;
}
 
public function setSomeData(a:Array):void{
    _someData = a;
    dispatchEvent(new Event("customDataChanged"));
}

But what I wanted to use is the Swiz autowire-by-property style which would look like this:

[Bindable]
[Autowire(bean="appModel", property="someData")]
public var someData:Array

So for the examle above I have a bean with id appModel defined in my IoC Container (BeanLoader) which contains the someData variable. Swiz wires the property into the presentation model implementation but how do I get my interface getter bindable?
The solution is quite easy. Just have a look at the generated actionscript with the compiler args -keep-generated-actionscript and you see that by default a PropertyChangeEvent is dispatched for bindable variables when they are changed. The type value of the event is “propertyChange” so the only thing I have to change in my interface is the event type:

[Bindable(event="propertyChange")]
function get someData():Array;

So my view gets the presentation model interface autowired-by-type:

[Bindable]
[Autowire]
public var model:IMyPresentationModel;
<s:List dataProvider="{model.someData}"/>

Now when the application model someData property changes, Swiz updates the autowired property which fires a PropertyChangeEvent and forces the binding to be updated in the view.