While building out a new framework for a series of highly form-centric applications in Flex 2 I ran into a strange problem. Seeing as I’m now using Flex I wanted to do things the right way and use a Validator to make sure that a value was selected. Imagine my surprise when the validation didn’t seem to happen. After some debugging and tracing through the Flex framework’s code I finally found that the Validator was firing and getting the correct result but failed to set the errorString property or fire the invalid event on the RadioButtonGroup being validated. Further tracing lead to the problem. The RadioButtonGroup was failing a test for “is IValidatorListener”. In other words, the RadioButtonGroup, which is conceptually a form element, does not respond at all to the events fired by a Validator.
Eventually through documentation and perusal of the RadioButtonGroup code I also realized that the RadioButtonGroup is not a UIComponent. This is understandable as the concept of a RadioButtonGroup is not linked to a specific layout of the radio buttons and the “group” really has no set physical presence. This explains why the IValidatorListener interface isn’t implemented in the same way as the other form elements as the UIComponent base class implements this for most of them. It doesn’t explain why the RadioButtonGroup does not implement it itself, however.
Of course you can always set the listener on the Validator to one of the radio buttons but I’d rather have all of the radio buttons show the error to let the user really know what’s happening.
To this end I created a RadioGroup class which implements IValidatorListener and sets the errorString and fires the valid/invalid events on each of the radios within the group.