協(xié)議定義了一個藍(lán)圖 規(guī)定了用來實(shí)現(xiàn)某一特定工作或者功能所必需的方法和屬性
類 結(jié)構(gòu)體 枚舉類型都可以遵循協(xié)議 并提供具體實(shí)現(xiàn)來完成定義的方法和功能

<code>protocol FullyName {
var fullName: String {get}
}
struct Person: FullyName {
var fullName: String
}
let john = Person(fullName: "John Appleseed")
print(john)
class Starship: FullyName{
var prefix1: String?
var name: String
init(name: String, prefix1: String){
self.name = name
self.prefix1 = prefix1
}
var fullName: String{
return (prefix1 == nil ?"" :prefix1!) + name
}
}
var ncc1701 = Starship(name: "Enterprise", prefix1: "USS")
print(ncc1701.fullName)
protocol RandomNumberGenerator {
func random() -> Double
}
class LinearcingryebntialGenerator: RandomNumberGenerator{
var lastRandom = 42.0
let m = 139968.0
let a = 3877.0
let c = 29573.0
func random() -> Double{
lastRandom = (lastRandom * a + c)%m
return lastRandom/m
}
}
let generator = LinearcingryebntialGenerator()
print("Here's a random number (generator.random())")
//協(xié)議類型
class Dice{
let sides: Int
let generator: RandomNumberGenerator
init(sides: Int, generator: RandomNumberGenerator){
self.sides = sides
self.generator = generator
}
func roll() -> Int{
return Int(generator.random()*Double(sides)) + 1
}
}
var d6 = Dice(sides: 6, generator: LinearcingryebntialGenerator())
for _ in 1...5{
print("Random dice roll is (d6.roll())")
}
//代理模式
protocol DiceGame {
var dice: Dice{get}
func play()
}
protocol DiceGameDelegate {
func gameDidStart(game: DiceGame)
func game(game: DiceGame, didStartNewTurnWithDiceRoll diceRoll: Int)
func gameDidEnd(game: DiceGame)
}
class SnakesAndLadders: DiceGame{
let finalSquare = 25
let dice = Dice(sides: 6, generator: LinearcingryebntialGenerator())
var square = 0
var board: [Int]
init(){
board = [Int](count: finalSquare + 1, repeatedValue: 0)
board[03] = +08; board[06] = +11; board[09] = +09; board[10] = +02;
board[14] = -10; board[19] = -11; board[22] = -02; board[24] = -08;
}
var delegate: DiceGameDelegate?
func play(){
square = 0
delegate?.gameDidStart(self)
gameloop: while square != finalSquare{
let diceRoll = dice.roll()
delegate?.game(self, didStartNewTurnWithDiceRoll: diceRoll)
switch square + diceRoll {
case finalSquare:
break gameloop
case let newSquare where newSquare > finalSquare:
continue gameloop
default:
square += diceRoll
square += board[square]
}}delegate?.gameDidEnd(self)
}
}
class DiceGameTracker: DiceGameDelegate{
var numberOfTurns = 0
func gameDidStart(game: DiceGame){
numberOfTurns = 0
if game is SnakesAndLadders{
print("Started a new game of Snakes and Ladders")
}
print("The game is using a (game.dice.sides)-sides dice")
}
func game(game: DiceGame, didStartNewTurnWithDiceRoll diceRoll: Int){
numberOfTurns += 1
print("Rolled a (diceRoll)")
}
func gameDidEnd(game: DiceGame){
print("The game lasted for (numberOfTurns) turns")
}
}
let tracker = DiceGameTracker()
let game = SnakesAndLadders()
game.delegate = tracker
game.play()
protocol TextRepresentable {
var textualDescription: String{get}
}
extension SnakesAndLadders: TextRepresentable {
var textualDescription: String{
return "A game of Snakes and Ladders with (finalSquare) squares"
}
}
//在擴(kuò)展中添加協(xié)議成員
extension Dice: TextRepresentable {
var textualDescription: String{
return "A (sides)-sided dice"
}
}
let d12 = Dice(sides: 12, generator: LinearcingryebntialGenerator())
print(d12.textualDescription)
//通過擴(kuò)展補(bǔ)充協(xié)議聲明
struct Hamster {
var name: String
var textualDescription: String{
return "A hamster named (name)"
}
}
extension Hamster: TextRepresentable {}
let simonTheHamster = Hamster(name: "Simon")
let somethingTextRepresentable: TextRepresentable = simonTheHamster
print(somethingTextRepresentable.textualDescription)
//協(xié)議類型的集合
let things: [TextRepresentable] = [game, d12, simonTheHamster]
for thing in things{
print(thing.textualDescription)
}
//協(xié)議的繼承
protocol PrettyTextRepresentable: TextRepresentable{
var prettyTextualDescription: String{get}
}
extension SnakesAndLadders {
var prettyTextualDescription: String{
var output = textualDescription + ":\n"
for index in 1...finalSquare{
switch board[index] {
case let ladder where ladder > 0:
output += "??"
case let snake where snake < 0:
output += "??"
default:
output += "??"
}
}
return output
}
}
print(game.prettyTextualDescription)
</code>

類專屬協(xié)議
添加class關(guān)鍵字 限制協(xié)議只能適配到class類型 不能適用到枚舉或者結(jié)構(gòu)體類型

協(xié)議合成
protocol<SomeProtocol, Anotherprotocol>
協(xié)議合成并不會生成一個新的協(xié)議 而是將多個協(xié)議合成為一個臨時的協(xié)議 超出范圍后立即失效

檢查協(xié)議的一致性
使用is和as操作符來檢查是否遵循某一協(xié)議或強(qiáng)制轉(zhuǎn)化為某一類型

可選協(xié)議
增加@objc標(biāo)識符 使用optional關(guān)鍵字

協(xié)議擴(kuò)展
使用extension 關(guān)鍵字 擴(kuò)展協(xié)議 并實(shí)現(xiàn)方法 所有協(xié)議都會擁有此方法
extension someProtocol{func A(){}}

為協(xié)議擴(kuò)展添加限制條件
使用where關(guān)鍵字進(jìn)行限制條件判斷