I am currently using databinding on a group of spark form elements and want to know if the data class I am bound to is dirty.
It might be nice if spark “Form” elements would trigger a change event that bubbled up to and was caught by a spark “Form”. Then I could just add an event listener to the form. But I don’t see something like that.
So besides comparing a copy of the original data class to the bound data class OR adding a change event to each form element and capturing that event, what’s an easy way of knowing a class object has changed?
Make an extension of TextInput or whatever other input elements you’ll have in your form then in your components creation complete register a listener for the change event, in the handler dispatch a bubbling event, then in your document that contains the form use your custom elements and add a listener via AS3 to the Form for the event you dispatched and stop it’s propagation at that point.
Otherwise I think your second solution of change handler on each wouldn’t be too bad. If you have a lot of elements in the form or it’s dynamic you could write a function that steps through the form items of the form and checks their children then you just have to write a switch that deals with each class type (you can use http://www.actionscriptdeveloper.co.uk/getting-the-class-of-an-object-in-as3/on each of the child elements to determine what type it is, then if it’s a TextInput or whatever register the appropriate event to call your commonly used function, just be sure it has a generic Event as it’s parameter since all other Events will be sub-classes thereof).
So far as I know there is no easy way to listen for changes to the underlying data from the ArrayCollection or other wrapper ListCollectionView data structures. Part of the problem is the elements added a collection aren’t required to implement any sort of interface to allow for listeners to be registered. That is, the data elements aren’t necessarily event dispatchers, the only other way for this information to be communicated to the List would be if the data elements had a handle on all lists that contain that element and they mark something on the lists to indicate “dirty” when any property is set. These are all achievable within the constraints of the language but aren’t provided out of the box as the usage for them is probably limited and could potentially unnecessarily bloat the cpu usage of the ListCollectionView in other cases.