1.用分類來對(duì)protocol中的方法進(jìn)行一些默認(rèn)實(shí)現(xiàn)

protocol Callable {
    var number:String {get set}
    func call()
}

extension Callable{
    func call(){
        print("撥打了電話\(self.number)")
    }
}

struct IPhone : Callable {
    var number: String = "110"
}

var iphone = IPhone()
iphone.call() //打印撥打了電話110

2.覆蓋protocol中的默認(rèn)實(shí)現(xiàn)

struct IPhone : Callable {
    var number: String = "120"
    func call() {
        print("用IPhone 8 撥打了電話\(self.number)")
    }
}
var iphone = IPhone()
iphone.call() //打印用iphone 8 撥打了電話120

3.一個(gè)類中同一個(gè)方法有兩份方法實(shí)現(xiàn)，你見過嗎？

我們把call的聲明從protocol中去除

protocol Callable {
    var number:String {get set}
}
extension Callable{
    func call(){
        print("撥打了電話\(self.number)")
    }
}

struct IPhone : Callable {
    var number: String = "119"
    func call() {
        print("用IPhone 9 撥打了電話\(self.number)")
    }
}

var iphone = IPhone()
iphone.call() //打印   用Iphone 9 撥打了電話119
(iphone as Callable).call() //打印 撥打了電話119

4.protocol中的選擇性默認(rèn)實(shí)現(xiàn)，6到不能行

protocol Callable {
    var number:String {get set}
    func call()
}
extension Callable{
    func call(){
        print("撥打了電話\(self.number)")
    }
}
protocol Netable {
    var ip :String {get set}
    func net()
}

extension Netable{
    func net(){
        print("我在上網(wǎng) ip\(self.ip)")
    }
}
extension Callable where Self:Netable{
    func call(){
        print("我在用網(wǎng)絡(luò)打電話 ip \(self.ip)")
    }
}
struct IPhone9 : Callable {
    var number: String = "110"
}
struct IPhone10 : Callable,Netable {
    var number: String = "110"
    var ip: String = "110.110.110.110"
}
var iphone9 = IPhone9()
iphone9.call() //打印 撥打了電話110

var iphone10 = IPhone10()
iphone10.call() //打印 我在用網(wǎng)絡(luò)打電話 ip 110.110.110.110