No logic in the visible attribute?

Question

FB 3.1
I have the following code which determines whether a button
should be displayed
<mx:Button id="nextButton" icon="{app.nextIcon}"
label="Next" visible="{wizard.selectedIndex < 0}"/>
I'm getting this error:
The value of attribute "visible" must not contain the '<'
character
I've found this bug which relates to the text attribute,
marked as Closed (Cannot Fix). It's not a serious bug in the
context of the "text" attribute but pretty serious with "visible"
attribute.

Answer 1

It's not clear from your post if you're trying to hide or
show the button if nothing is selected, but here's how you can do
it either way:
Show the button whenever an item is selected (selectedIndex
is greater than -1).
visible="{dg.selectedIndex != -1}"
Hide the button when no item is selected (selectedIndex is
-1).
visible="{dg.selectedIndex == -1}"
This also works great on the enabled property if you want to
see the button but have it grayed out.
fyi any non-zero number is TRUE when cast to Boolean:
-1 = TRUE
0 = FALSE
1 = TRUE