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A common complaint among Flex component developers is that too many of the methods in the Flex component framework are marked private instead of protected. Here’s why I’m making that complaint again today:

What I wanted to do
I wanted to make a component called SideStack that extends ViewStack. The SideStack would layout its children like an HBox by using the BoxLayout utility class. I wanted to extend ViewStack because it already has a lot of the other features I wanted: history management, the ability for developers to add children declaritively in MXML, deferred instantiation, etc.

When the user would change the selectedChild, I would leave the previously selectedChild visible and use AnimateProperty to slide the newly selectedChild into position. The layout part worked great, but preventing the previously selected child from being hidden is where the problems started.

Why I couldn’t do it the way I wanted
In ViewStack.commitProperties, there’s a call to a private method called commitSelectedIndex. This is where the previousChild.setVisible( false ) happens. Unfortunately, the commitSelectedIndex method is marked private, so I can’t override it. That started the following frustrating process:

Failed work-around #1
My first thought was, “Well, I’ll just override commitProperties, copy the stuff I need from ViewStack.commitProperties, and I’m good.” The problem is, I need to prevent the code in ViewStack.commitProperties from running but I need Container.commitProperties to execute. In other words, instead of this:

//SideStack.as

override protected function commitProperties():void
{
super.commitProperties();

//copied & modified code from ViewStack.commitProperties
}

I would need to do something impossible, like this:

override protected function commitProperties():void
{
super.super.commitProperties();

//copied & modified code from ViewStack.commitProperties
}

So, back to the drawing board.

Failed work-around #2
My next try was to temporarily set the flag that causes commitSelectedIndex to get called to a value that would cause that block to get skipped. In other words, I would set proposedSelectedIndex to -1 before I called super.commitProperties(). Nope. proposedSelectedIndex is private too, so I can’t do that.

Crazy, ugly work-around attempt #3
Out of frustration, I decided to copy & paste all the ViewStack code into my SideStack class instead of extending it. I know, I know. But I can’t do that because I want to be able to bind the dataProvider of a ButtonBar, LinkBar, or TabBar to the component and that would require a ViewStack or a subclass.

Pending ugly work-around attempt #4
Once I take a little break, I’m going to try to do previousChild.setVisible( true ) after ViewStack sets it to false. That might get me a little bit further, but I’m afraid of another roadblock. And that’s a fairly ugly hack.

If that fails
I’ll give up and just use a different version that extends HBox and, over time, I’ll add the features like historyManagement and stuff later.

If the framework was open source right now
I would be tempted to just edit ViewStack.as and change commitSelectedIndex to protected, but then I’d be the only one that could use my component.

Anybody have a magic solution?

Any Adobe engineers care to comment?