Importing Packages in AS3

Even the most simple task seems to take me forever in Flex, since I have to troll through reams of documentation to make sure I understand the concepts involved. This morning I came across something in one of my references that went something like this:

"Because this class is in the same package as the other class you want to use, you don't need to add an import statement in order to use it."

I went through reams of documentation looking for something to verify this, but couldn't. Finally, someone on a Google Group I belong to posted this quote from Colin Moock's Essential Actionscript 3.0.

"Code in a given package can refer to the classes in that package by their unqualified names... To gain access to a class in another package, we use the import directive..."

So yes, it's true. You don't have to import classes in the same package as the one where you are working.

Easy when you know how

I think I spent a couple of hours yesterday scouring the Flex docs to figure out how to make a tab on a TabNavigator disabled. And it seems like I'm not the only one. After messing with it for a while, I decided to set the enabled property on the child form to false. Which worked.

I went back to the docs and discovered that it had been there all the time:

If you disable a child of a TabNavigator container by setting its enabled property to false, you also disable the associated tab.

Weird, because I know I searched the TabNavigator help page for the word "disable" like a million times.

Comparing XML nodes of the same name with E4X

I recently found a situation that the Flex E4X documentation didn't cover, and I couldn't find an example for ActionScript 3 or JavaScript that covered it. Essentially, I had XML in the data property of an itemRenderer that looked something like this:

<question id="1>
<selected>
1
</selected>
<selected>
5
</selected>
</question>

Essentially, my itemRenderer has five buttons (A-E), any or all of which can be selected. If the user clicks one of the buttons and it is already selected, it should be deselected. Or, in other words, if there is already an element in the data XML's "selected" collection with the same value as what the user clicked (assuming A=1 and E=5), then that element should be deleted.

I had a challenge, though, in that I didn't want to use a for loop. I was using XML, and E4X should be able to handle this easily. The problem I had was that every E4X example I found that referenced the contents of the nodes of an XML node presumed that there would only be one of each node of the same node. So if my XML structure had been

<question id="1>
<selected>
1
</selected>
</question>

then life would have been easy. I could have used data.(selected==userSelection) and away I'd go. But the problem when you have multiple nodes named "selected" is that data.selected returns an XMLList that contains all of the nodes. Hence, it cannot be equal to any single number, even though when there is only one node it works fine.

So, after much research, I came up with something like this:

myXMLNode:XML="<selected>"+userSelection+"</selected>";
if (data.selected.contains(myXMLNode){
//loop through and delete any nodes with that value
} else {
//add a node of that value
}

I wasn't really happy with this, and I posted to the Flex Coders mailing list. Tracy Spratt suggested that I use the text() method of the XML object, so I wound up with something like this in my final logic:

if (data.selected.(text()==userSelection).length()==0){
//add the selected node to the data object
data.prependChild(myXMLNode);
} else {
//remove the selected node from the data object
for (i=data.selected.length()-1; i>=0; i--){
if (data.selected[i] == userSelection){
delete data.selected[i];
}

I hope this will help someone else solve this problem without having to waste as much time as I spent on this!

Debugger and E4X

I had a thingie that I had built in Flex, and I wanted to change it from showing a property of the xml object passed in the data object to the itemRenderer to iterating through child nodes of the xml object to show multiple selections. I thought my problem was with the E4X expression, so I wanted to be able to quickly change the E4X syntax without having to recompile and run my project again. So I decided I'd create a watch expression with my E4X in it and just keep trying until I got it right.

It seemed that no matter what I tried, I kept getting "Errors in Evaluation" for my E4X expression. Finally, in frustration, I put my best guess at the E4X expression in a trace expression, and it worked like a charm. The actual problem was that the logic wasn't even going into the piece I thought it was. So let that be a lesson to me that the debugger expressions window can't actually evaluate E4X!

Oh, and if anyone knows something in the debugger that works like the Immediate pane in VBA, please let me know!