Here's the scenario. A protocol Paintable requires a property primaryColor with a getter and setter.
protocol Paintable {
var primaryColor: UIColor { get set }
}Paintable is extended to provide a default getter and setter for primaryColor.
extension Paintable {
var primaryColor: UIColor {
get { return UIColor.blackColor() }
set { }
}
}The empty setter is necessary. Otherwise, an adopting type that does not implement primaryColor gets the "does not conform to protocol" error. So this would lead me to believe that, by writing the empty setter, the protocol requirements are satisfied.
However, in a type that adopts Paintable but does not implement primaryColor, the getter works fine, but attempting to set primaryColor gets an error.
class Car: Paintable {
func paintNewColor(color: UIColor) {
print(primaryColor) // Works fine
primaryColor = color // Generates error: cannot assign to property: 'self' is immutable
}
}Of course, if Car implements primaryColor as a variable, the setter works fine.
class Car: Paintable {
var primaryColor = UIColor.whiteColor()
func paintNewColor(color: UIColor) {
print(primaryColor) // Works fine
primaryColor = color // Works fine
}
}Is this intended behavior?
