我有两个协议:Pen 和 InstrumentForProfessional。我希望使任何一个Pen成为一个InstrumentForProfessional:
protocol Pen {
var title: String {get}
var color: UIColor {get}
}
protocol Watch {} // Also Instrument for professional
protocol Tiger {} // Not an instrument
protocol InstrumentForProfessional {
var title: String {get}
}
class ApplePen: Pen {
var title: String = "CodePen"
var color: UIColor = .blue
}
extension Pen: InstrumentForProfessional {} // Unable to make ApplePen an Instument for Professional: Extension of protocol Pen cannot have an inheritance clause
let pen = ApplePen() as InstrumentForProfessional