Swift 继承Inheritance

// 重写方法class Train: Vehicle {    overrIDe func makeNoise() {        print("Choo Choo")    }}let train = Train()train.makeNoise()// Choo Choo

// 重写属性class SpeedlimitedCar: Vehicle {    overrIDe var currentSpeed: Double  {        get {            return super.currentSpeed        }        set {            super.currentSpeed = min(newValue,40.0)        }    }}let limitedCar = SpeedlimitedCar()limitedCar.currentSpeed = 60.0print("SpeedlimitedCar: \(limitedCar.description)")// SpeedlimitedCar: traverling at 40.0 miles per hour

class Car: Vehicle {    var gear = 1    overrIDe var description: String {        return super.description + " in gear \(gear)"    }}let car = Car()car.currentSpeed = 25.0car.gear = 3print("Car: \(car.description)")// Car: traverling at 25.0 miles per hour in gear 3// 重写属性监视器class automaticCar: Car {    overrIDe var currentSpeed: Double {        dIDSet {            gear = Int(currentSpeed / 10.0) + 1        }    }}let automatic = automaticCar()automatic.currentSpeed = 35.0print("automaticCar: \(automatic.description)")// automaticCar: traverling at 35.0 miles per hour in gear 4

防止重写可以在属性,方法或是类,前面加上关键字final.@H_502_13@@H_502_13@

You can prevent a method,property,or subscript from being overrIDden by marking it asfinal@H_502_13@. Do this by writing thefinalmodifIEr before the method,or subscript’s introducer keyword (such asfinal var,final func,monospace; word-wrap:break-word">final class func,andfinal subscript).

Any attempt to overrIDe a final method,or subscript in a subclass is reported as a compile-time error. Methods,propertIEs,or subscripts that you add to a class in an extension can also be marked as final within the extension’s deFinition.

You can mark an entire class as final by writing thefinalmodifIEr before theclasskeyword in its class deFinition (final class). Any attempt to subclass a final class is reported as a compile-time error.

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