Question

我想知道是否可以初始化嵌套类，例如初始化汽车时设定轮胎压力：

class Tyre {
    var pressure : Double = 0.0

    init() { }

    init(withPressure p: Double) {
        self.pressure = p
    }
}

class Car {
    var tyre = Tyre()
}

// should return 2.5
let myCar = Car().tyre(withPressure : 2.5).pressure

现在只有这个有效，使用默认的init（）：

let myCar = Car().tyre.pressure  // return 0.0

提前感谢您的回复！

Answer 1

你可以做到这一点，但你可以将自定义轮胎作为参数传递给你的汽车的初始值：

class Tyre {
    var pressure : Double = 0.0

    init() { }

    init(withPressure p: Double) {
        self.pressure = p
    }
}

class Car {
    var tyre: Tyre!

    init(withTyre t: Tyre) {
        self.tyre = t
    }
}

let myCar = Car(withTyre: Tyre(withPressure : 2.5))

// should return 2.5
let pressure = myCar.tyre.pressure

Answer 2

您必须单独初始化tyre。你可以用两种方式做到这一点。 Car可以采用类型压力参数：

class Car {
    var tyre

    init(withTyrePressure tyrePressure: Double) {
        tyre = Tyre(withPressure: tyrePressure)
    }
}

或Car可以使用tyre参数：

class Car {
    var tyre

    init(withTyre tyre: Tyre) {
        self.tyre = tyre
    }
}

let tyre = Tyre(withPressure: 2.5)
let car = Car(withTyre: tyre)

Answer 3

class Tyre {
    var pressure : Double = 0.0

    init() { }

    init(withPressure p: Double) {
        self.pressure = p
    }
}

class Car {
    var tyre : Tyre
    init(withPressure p:Double) { // <-- this is the only change from your code
        self.tyre = Tyre(withPressure:p)
    }
}

// should return 2.5
let myCar = Car(withPressure : 2.5)
myCar.tyre.pressure // 2.5

Answer 4

class Tyre {
    var pressure : Double = 0.0

    init() { }

    init(withPressure p: Double) {
        self.pressure = p
    }
}

class Car {
    var tyre = Tyre()
}

// should return 2.5
let myCar = Car()

myCar.tyre = Tyre(withPressure: 2.5)

print(myCar.tyre.pressure)

Answer 5

我找到了我的问题的答案但是必须通过使用返回Tire类而不是使用属性的函数轮胎来更改Car类。所以可以完成！ ; - ）

以下示例可能没有意义，但只是原理的证明......

class Tyre {
    var pressure : Double = 0.0

    init() { }

    init(withPressure p: Double) {
        self.pressure = p
    }
}

class Car {
    //var tyre = Tyre(withPressure: 2.5)

    func tyre (withPressure p: Double) -> Tyre {
        return Tyre(withPressure: p)
    }
}


let myCar = Car().tyre(withPressure: 2.2).pressure

Swift：初始化一个嵌套类

5 个答案: