如何覆盖超类中的私有var

Question

所以我有以下超类:

class Vehicle {

    private var _maxSpeed: Int = 100

    var maxSpeed: Int {
        get {
            return _maxSpeed
        }

var tooFast: Bool {
        get {
            if maxSpeed >= 140 {
                return false
            } else {
                return true
            }
        }
    }
}

另外,我有一些子类,我想覆盖maxSpeed ...每个例子:

class SuperCar: Vehicle {
//override the maxspeed...

}

但是我应该怎么做呢？或者,如果我们不将其设为私有,这是否可行？我试图将私有部分扔出窗外,但这不会起作用......

class Vehicle {

    var maxSpeed: Int = 100

var tooFast: Bool {
        get {
            if maxSpeed >= 140 {
                return false
            } else {
                return true
            }
        }
    }
}

class SuperCar: Vehicle {
// override the maxSpeed...
override var maxSpeed: Int = 200
// Will not work...
}

Answer 1

只需将类和子类放在同一个文件中即可.private与继承无关.它与文件范围有关.同一文件中的任何内容都可以访问private成员.

也就是说,你几乎肯定不应该在这里使用继承.Vehicle应该几乎肯定是一个协议.那么你就不会有任何继承或头痛private.

protocol Vehicle {
    var maxSpeed: Int {get}
}

extension Vehicle {
    // Default implementation if none is given
    var maxSpeed: Int { return 100 }

    // Another method that applies to all Vehicles
    var tooFast: Bool {
        return maxSpeed < 140 // (feels like this should be >= 140, but matching your code)
    }
}

struct SuperCar: Vehicle {
    // override the default implementation for the protcocol
    var maxSpeed = 200
}