swift - 如何在其子类中修改类的属性？

Question

class Animals{
    var name : String = "default"
    var age : Int = 0
    func Details()-> String{
        return "This animal is a \(name) and has \(age) years old."
    }
}


class Dogs : Animals{
    name = "dog"
}

class Cats : Animals{
    name = "cat"
}

var MyAnimal = Dogs()

我想看到这条消息:“这只动物是一只狗，已经 0 岁了。” 但是每次我收到这个:“这只动物是默认的并且有 0 岁。”

var HisAnimal = Cats()

Answer 1

如果您想要存储属性而不是计算属性，您可以在初始化程序 中设置name，如下所示:

class Animal {
    let name: String
    var age: Int = 0
    /* designated initializer: fully initializes all instance properties */
    init(name: String) {
        self.name = name
    }
    func details() -> String {
        return "This animal is a \(name) and has \(age) years old."
    }
}


class Dog : Animal {
    /* designated initializer of subclass: must call a designated
       initializer from its immediate superclass                   */
    init() {
        super.init(name: "dog")
    }
}

class Cat : Animal {
    /* ... */
    init() {
        super.init(name: "cat")
    }
}

let myAnimal = Dog()

这种机制确保 name 仅从一个地方设置，并显式传递给初始化程序。