Spark lifecycle changes between Flex 4.5 and 4.6

Question

I have recently migrated some of my projects to the shiny new Flex 4.6 SDK. I wasn't expecting much trouble since it was only a minor release. But as a matter of fact I got hundreds of errors all over the place. These errors would mostly come from Spark SkinnableComponents; for example:

override protected function getCurrentSkinState():String {
    return mySkinPart.someProperty ? "normal" : "someOtherState";
}

would work just fine under 4.5, but would throw me a nullpointer error in 4.6. The reason is simple enough: in 4.6 getCurrentSkinState() is called before the skinparts are created, whereas in 4.5 I could be certain that the skinparts in the default state would be there.

Further investigation led me to believe that the initial state of a Skin is now undefined instead of the first state in the States array (until it calls getCurrentSkinState() that is).

Fixing these problems is usually pretty easy and requires just somewhat more defensive programming from my part. But that's not my real issue.

The real issue is that if the component lifecycle has changed, I'd like to know exactly what has changed and what parts of my projects might be affected.

I would be very appreciative if someone could shed some light on this or at least point me to the right place where I can read all about it (because the only release notes I could find were only covering the new mobile components).

---

Edit (this doesn't change the question; I just wanted to share my findings with you)

Another issue I just ran into: the dynamic modifier seems to no longer be inherited by subclasses. This is a pure ActionScript issue, so I guess it's the compiler that treats it differently.

Let me explain. Consider this class:

public class MyClass extends Array { }

Now, if I try to push a new item into this custom Array like this:

var t:Array = new MyClass();
t.push("hello");

• SDK 4.5.1: no problem
• SDK 4.6: "Cannot create property 0 on MyClass" at runtime

Apparently that's because Array is dynamic and MyClass isn't, so it's easily fixed:

public dynamic class MyClass extends Array { }

and the error's gone.

But what if I used a third-party library that has code like this and to which I had no source code access? My application would break and there's no way I could fix it. I mean: come on, that's no minor change for a dot-release.

Answer 1

I think there are two questions in there.

1 ) The real issue is that if the component lifecycle has changed, I'd like to know exactly what has changed and what parts of my projects might be affected.

I haven't seen a comprehensive low-level analysis of the differences between the two version. If you are really concerned, and you have the time to spare, you could use a diff tool to compare the source code for the two SDK's. There shouldn't be too many major structural changes - e.g. renamed classes or packages, so it might not be so bad. I expect a lot of classes won't have changed at all.

2 ) Another issue I just ran into: the dynamic modifier seems to no longer be inherited by subclasses. This is a pure ActionScript issue, so I guess it's the compiler that treats it differently.

This one is easier. dynamic has never been inherited. Object is dynamic, so if the attribute was inherited every class would have to be dynamic too.

If there appears to be a change in behaviour related to dynamic class instances, then there is something else going on in your code.