How to define a property set by getter and seter can be bound

// Define private variable for maxfontsize.
Public VaR _ maxfontsize: Number = 15;
// Define public getter method, mark the property
// As usable for the source of data binding,
// And specify the name of the binding event.
[Bindable ("maxfontsizechanged")]
Public Function get maxfontsize (): number {
Return _ maxfontsize;
}
// Define public setter method.
Public Function set maxfontsize (value: Number): void {
If (value <= 30 ){
_ Maxfontsize = value;
} Else _ maxfontsize = 30;
// Dispatch the event to trigger data binding.
Dispatchevent (new event ("maxfontsizechanged "));
}