Dependent text fields - actionscript-3

Question

I want to have text fields which are dependent of each other. E.g there's two input text fields like angular frequency(ω) and ordinary frequency(f), ω=2πf. If I change one, the other changes. How can I do that? Second thing, how can I check if text field is empty?
if (field.text=="")... // doesn't work

Answer 1

There are 2 ways of doing this. You can either have some sort of update function that is called at every frame checking for the current value of each field with what they used to be and seeing if something changed then react to that.
private var tf1 : TextField = new TextField();
private var tf2 : TextField = new TextField();
private var tf1LastVal : String = "";
private var tf2LastVal : String = "";
public function update() : void
{
if(tf1.text != tf1LastVal)
{
tf2.text = //put your logic here
tf1LastVal = tf1.text;
}
else if(tf2.text != tf2LastVal)
{
tf1.text = //put your logic here
tf2LastVal = tf2.text;
}
}
The other, and better way (in my opinion) of doing this is by adding event listeners to your TextFields
//add this where you construct your TextFields
tf1.addEventListener(Event.CHANGE, onTf1Change);
tf2.addEventListener(Event.CHANGE, onTf2Change);
//end
private function onTf1Change(e : Event) : void
{
tf2.text = //your logic here;
}
private function onTf2Change(e : Event) : void
{
tf1.text = //your logic here;
}