Swift 继承 v.s 调用 super

Question

我正在学习 Swift 编程语言中的以下章节：

If your subclass doesn’t define any designated initializers, it automatically inherits all of its superclass designated initializers.

然后我在我的目标中尝试了这些代码：

class Car {
    var name: String = "Unknown"
    init(name: String) {
        self.name = name
    }
}
class RacingCar: Car {
    var speed = 0.0
    init(name: String, speed: Double) {
        self.speed = speed
        super.init(name: name)//this is where I got confused
    }
}

根据规则一，RacingCar class 不会从它的 superclass Car 继承 init(name:) 指定的初始化器。但是，我仍然可以在我的 subclass 中调用 super.init(name:)。怎么会这样？我对此很困惑。谁能解释为什么？谢谢

Answer 1

继承初始化器意味着该初始化器可用于您的子类的实例（这就是继承的含义）；也就是说，您的子类的初始化程序可以在 self:

上调用它

class RacingCar: Car {
    var speed = 0.0
    init(name: String, speed: Double) {
        self.speed = speed
        self.init(name: name) // <-- Error: This initializer is not inherited
    }
}

您无需继承构造器即可在 super 上调用它：超类不会因为您对其进行子类化而失去对其构造器的访问权限。

class RacingCar: Car {
    var speed = 0.0
    init(name: String, speed: Double) {
        self.speed = speed
        super.init(name: name) // <-- Works: super class does have this initializer
    }
}

Swift 继承 v.s 调用 super

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