The Space For App Developers

Today I passed Flex 4 ACE exam. I made a very decent score of 93% with following distribution in the exam sections:

• Creating a User Interface (UI) 85%
• Flex system architecture and design 100%
• Programming Flex applications with ActionScript 100%
• Interacting with data sources and servers 87%
• Using Flex in Adobe AIR 100%

To prepare for the exam I used Attest3, I went through the mock tests 3 or 4 times and at the same time I used Flex 4 help and ActionScript 3 docs as a reference. I encourage anyone to take the exam as it gives you a good overview of your Flex/AIR knowledge.

I wanted to share a video recording with an un-framework overview. This simple library has evolved a little bit from my previous post but I expect it will stay in this form for good I don’t think it can evolve to anything more sophisticated but I hope that it will serve as an inspiration to others when building their own sets of helpers. I plan to use it solely as a substitue for my favorite DI frameworks when doing mobile Flex development.

Those who know me or at least subscribe to my blog know that I’m a big fan of Flex/AS3 frameworks. At this year’s Adobe MAX conference I even had my own session where I covered five major DI frameworks. Usually these frameworks provide a lot of productivity features and helpers like: IoC/DI, Event/Messaging bus, implementation of some architectural or design patterns (MVC, Command…), and many others. But what happens if we can’t or don’t want to use any of these frameworks?

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Recently I was looking for an easy way to extend my existing model objects with additional properties. The problem I had was that there was no option to mark these model classes as dynamic. What I came up with was a solution that uses the ObjectProxy class that comes with Flex. ObjectProxy essentially is a class that allows you to track property changes of its wrapped object. So what I also got with this approach was an ability to register a PropertyChangeEvent handler with my model objects.

The snippet below shows how I extend my User class object with an additional selected property. This is a view specific property so it wouldn’t really be a good practice to do it directly in the model.

	// Wrapping each user into ObjectProxy with selected additional property selected 
	var userProxy:ObjectProxy = new ObjectProxy({user:user, selected:false});
	// Registering event PROPERTY_CHANGE handle
	userProxy.addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, 
		userProxy_propertyChangeHandler);

Below is a reason why I needed all that and how it works in practice; you can right-click the example to view the source code. BTW: If you are looking for a simple and quick way to have a dynamic Checkbox List this a way to go.

Another thing that the ObjectProxy class can resolve is a very common warning that occurs when you try to bind to not bindable properties: warning: unable to bind to property 'foo' on class 'Object' (class is not an IEventDispatcher).