[Swift 官方教程]13 继承

定义基类 (Defining a Base Class)

class Pet {
    var name: String = "Pet"
    var age = 0.0
    var description: String {
        return "My name is \(name), I'm \(age) years old."
    }
    
    func eat() {
    }
}

子类 (Subclassing)

class Cat: Pet {
    var value = 18.4
}

let cat = Cat()
cat.name = "mimi"
cat.age = 2.3
print(cat.description)

重写 (Overriding)

使用 override

访问超类的方法, 属性和下标 (Accessing Superclass Methods, Properties, and Subscripts)

使用 super:

方法: super.method()
属性: super.properties
下标: super[index]

重写方法 (Overriding Methods)

class Dog: Pet {
    override func eat() {
        print("I like bones.")
    }
}
let dog = Dog()
dog.eat()

重写属性 (Overriding Properties)

重写属性的 Getters 和 Setters (Overriding Property Getters and Setters)

判断是否属于重写的依据是属性名和其类型:

class Rabbit: Pet {
    var color = "white"
    override var description: String {
        return super.description + "My color is \(color)"
    }
}

let rabbit = Rabbit()
rabbit.name = "Nity"
rabbit.age = 1.5
print(rabbit.description)

重写属性观察器 (Overriding Property Observers)

class Pig: Pet {
    var weight = 1.8
    override var age: Double {
        didSet {
            weight = weight * age
        }
    }
}

let pig = Pig()
pig.age = 10
print(pig.weight)

防止被重写 (Preventing Overrides)

使用 final