Swift5.1学习随笔之多态

多态的实现原理：

• OC：Runtime
• C++：虚表（虚函数表）
• Swift：纯Swift没有Runtime，更加接近虚表的实现

class Animal {
    func speak() {
        print("Animal speak")
    }
    func eat() {
        print("Animal eat")
    }
    func sleep() {
        print("Animal sleep")
    }
}

class Dog: Animal {
    override func speak() {
        print("Dog speak")
    }
    override func eat() {
        print("Dog eat")
    }
    func run() {
        print("Dog run")
    }
}

var a = Animal()
a.speak() // Animal speak
a.eat() // Animal eat
a.sleep() // Animal sleep
print("******************")
var d = Dog()
d.speak() // Dog speak
d.eat() // Dog eat
d.sleep() // Animal sleep
d.run() // Dog run

上面的代码写法都看得懂，看下下面的写法：

var a = Animal()
a.speak() // Animal speak
a.eat() // Animal eat
a.sleep() // Animal sleep
print("******************")
//多态：父类指针指向子类对象
a = Dog()
a.speak() // Dog speak
a.eat() // Dog eat
a.sleep() // Animal sleep