Pseudo static variables in Flash/Flex
The other day I was running into an odd issue. I’ve developed a Flex component and inherited two other components from this parent component. In the parent component I’ve defined a private variable inside of an mx:Script block:
private var myDataArray = new Array();
Additionally the parent component offered a private function to push objects into that array.
I created instances of the two sub-classed components and called the private function of the parent component to fill the instance variables (well, I thought they were instance variables 
.
What happened was that both instances of my sub-classed components shared the same variable, because all the data I put into one was visible for the other one as well and vice versa. The variable behaved like a static variable in Java. It was not too difficult to find the error (the initialisation of the array didn’t take place in the constructor as it should have, aaaargs), but I wondered why the hell Flex did create this pseudo-static class variable until Aral told me that this is some sort of AS 1 Flash Player relict. Good to know, but a weird behaviour
This is why:
AS2:
private var myDataArray = new Array();
AS1:
MyClass.prototype.myDataArray = new Array();
So when you create a few instances of my class, they all refer to the same object on the Class’s prototype.
Hey Kai, it’s these little things that make life interesting for us in the Flash world!