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更新示例代码 println() -> print()

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futantan
2015-06-29 19:02:28 +08:00
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source/chapter2/22_Protocols.md
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@ -1,4 +1,4 @@
> 翻译：[geek5nan](https://github.com/geek5nan) > 翻译：[geek5nan](https://github.com/geek5nan)
> 校对：[dabing1022](https://github.com/dabing1022) > 校对：[dabing1022](https://github.com/dabing1022)
# 协议 # 协议
@ -164,9 +164,9 @@ class LinearCongruentialGenerator: RandomNumberGenerator {
} }
} }
let generator = LinearCongruentialGenerator() let generator = LinearCongruentialGenerator()
println("Here's a random number: \(generator.random())") print("Here's a random number: \(generator.random())")
// 输出 : "Here's a random number: 0.37464991998171" // 输出 : "Here's a random number: 0.37464991998171"
println("And another one: \(generator.random())") print("And another one: \(generator.random())")
// 输出 : "And another one: 0.729023776863283" // 输出 : "And another one: 0.729023776863283"
``` ```
@ -178,7 +178,7 @@ println("And another one: \(generator.random())")
如果协议中的实例方法打算改变其`遵循者`实例的类型，那么在协议定义时需要在方法前加`mutating`关键字，才能使`结构体，枚举`来采用并满足协议中对方法的规定。 如果协议中的实例方法打算改变其`遵循者`实例的类型，那么在协议定义时需要在方法前加`mutating`关键字，才能使`结构体，枚举`来采用并满足协议中对方法的规定。
>注意: >注意:
>用`类`实现协议中的`mutating`方法时，不用写`mutating`关键字;用`结构体`，`枚举`实现协议中的`mutating`方法时，必须写`mutating`关键字。 >用`类`实现协议中的`mutating`方法时，不用写`mutating`关键字;用`结构体`，`枚举`实现协议中的`mutating`方法时，必须写`mutating`关键字。
如下所示，`Togglable`协议含有名为`toggle`的突变实例方法。根据名称推测，`toggle`方法应该是用于切换或恢复其`遵循者`实例或其属性的类型。 如下所示，`Togglable`协议含有名为`toggle`的突变实例方法。根据名称推测，`toggle`方法应该是用于切换或恢复其`遵循者`实例或其属性的类型。
@ -255,7 +255,7 @@ class SomeSuperClass {
} }
} }
class SomeSubClass: SomeSuperClass, SomeProtocol { class SomeSubClass: SomeSuperClass, SomeProtocol {
// "required" from SomeProtocol conformance; "override" from SomeSuperClass // "required" from SomeProtocol conformance; "override" from SomeSuperClass
required override init() { required override init() {
@ -277,7 +277,7 @@ class SomeSubClass: SomeSuperClass, SomeProtocol {
尽管`协议`本身并不实现任何功能，但是`协议`可以被当做类型来使用。 尽管`协议`本身并不实现任何功能，但是`协议`可以被当做类型来使用。
使用场景: 使用场景:
* `协议类型`作为函数、方法或构造器中的参数类型或返回值类型 * `协议类型`作为函数、方法或构造器中的参数类型或返回值类型
* `协议类型`作为常量、变量或属性的类型 * `协议类型`作为常量、变量或属性的类型
@ -314,7 +314,7 @@ class Dice {
```swift ```swift
var d6 = Dice(sides: 6,generator: LinearCongruentialGenerator()) var d6 = Dice(sides: 6,generator: LinearCongruentialGenerator())
for _ in 1...5 { for _ in 1...5 {
println("Random dice roll is \(d6.roll())") print("Random dice roll is \(d6.roll())")
} }
//输出结果 //输出结果
//Random dice roll is 3 //Random dice roll is 3
@ -333,7 +333,7 @@ for _ in 1...5 {
委托模式可以用来响应特定的动作或接收外部数据源提供的数据，而无需要知道外部数据源的所属类型(*译者注:只要求外部数据源`遵循`某协议*)。 委托模式可以用来响应特定的动作或接收外部数据源提供的数据，而无需要知道外部数据源的所属类型(*译者注:只要求外部数据源`遵循`某协议*)。
下文是两个基于骰子游戏的协议: 下文是两个基于骰子游戏的协议:
```swift ```swift
protocol DiceGame { protocol DiceGame {
@ -349,7 +349,7 @@ protocol DiceGameDelegate {
``` ```
`DiceGame`协议可以在任意含有骰子的游戏中实现，`DiceGameDelegate`协议可以用来追踪`DiceGame`的游戏过程 `DiceGame`协议可以在任意含有骰子的游戏中实现，`DiceGameDelegate`协议可以用来追踪`DiceGame`的游戏过程
如下所示，`SnakesAndLadders`是`Snakes and Ladders`(译者注:[Control Flow](2)章节有该游戏的详细介绍)游戏的新版本。新版本使用`Dice`作为骰子，并且实现了`DiceGame`和`DiceGameDelegate`协议，后者用来记录游戏的过程: 如下所示，`SnakesAndLadders`是`Snakes and Ladders`(译者注:[Control Flow](2)章节有该游戏的详细介绍)游戏的新版本。新版本使用`Dice`作为骰子，并且实现了`DiceGame`和`DiceGameDelegate`协议，后者用来记录游戏的过程:
```swift ```swift
@ -403,16 +403,16 @@ class DiceGameTracker: DiceGameDelegate {
func gameDidStart(game: DiceGame) { func gameDidStart(game: DiceGame) {
numberOfTurns = 0 numberOfTurns = 0
if game is SnakesAndLadders { if game is SnakesAndLadders {
println("Started a new game of Snakes and Ladders") print("Started a new game of Snakes and Ladders")
} }
println("The game is using a \(game.dice.sides)-sided dice") print("The game is using a \(game.dice.sides)-sided dice")
} }
func game(game: DiceGame, didStartNewTurnWithDiceRoll diceRoll: Int) { func game(game: DiceGame, didStartNewTurnWithDiceRoll diceRoll: Int) {
++numberOfTurns ++numberOfTurns
println("Rolled a \(diceRoll)") print("Rolled a \(diceRoll)")
} }
func gameDidEnd(game: DiceGame) { func gameDidEnd(game: DiceGame) {
println("The game lasted for \(numberOfTurns) turns") print("The game lasted for \(numberOfTurns) turns")
} }
} }
``` ```
@ -468,7 +468,7 @@ extension Dice: TextRepresentable {
```swift ```swift
let d12 = Dice(sides: 12,generator: LinearCongruentialGenerator()) let d12 = Dice(sides: 12,generator: LinearCongruentialGenerator())
println(d12.asText()) print(d12.asText())
// 输出 "A 12-sided dice" // 输出 "A 12-sided dice"
``` ```
@ -480,7 +480,7 @@ extension SnakesAndLadders: TextRepresentable {
return "A game of Snakes and Ladders with \(finalSquare) squares" return "A game of Snakes and Ladders with \(finalSquare) squares"
} }
} }
println(game.asText()) print(game.asText())
// 输出 "A game of Snakes and Ladders with 25 squares" // 输出 "A game of Snakes and Ladders with 25 squares"
``` ```
@ -504,7 +504,7 @@ extension Hamster: TextRepresentable {}
```swift ```swift
let simonTheHamster = Hamster(name: "Simon") let simonTheHamster = Hamster(name: "Simon")
let somethingTextRepresentable: TextRepresentable = simonTheHamster let somethingTextRepresentable: TextRepresentable = simonTheHamster
println(somethingTextRepresentable.asText()) print(somethingTextRepresentable.asText())
// 输出 "A hamster named Simon" // 输出 "A hamster named Simon"
``` ```
@ -523,7 +523,7 @@ let things: [TextRepresentable] = [game,d12,simonTheHamster]
```swift ```swift
for thing in things { for thing in things {
println(thing.asText()) print(thing.asText())
} }
// A game of Snakes and Ladders with 25 squares // A game of Snakes and Ladders with 25 squares
// A 12-sided dice // A 12-sided dice
@ -583,7 +583,7 @@ extension SnakesAndLadders: PrettyTextRepresentable {
任意`SankesAndLadders`的实例都可以使用`asPrettyText()`方法。 任意`SankesAndLadders`的实例都可以使用`asPrettyText()`方法。
```swift ```swift
println(game.asPrettyText()) print(game.asPrettyText())
// A game of Snakes and Ladders with 25 squares: // A game of Snakes and Ladders with 25 squares:
// ○ ○ ▲ ○ ○ ▲ ○ ○ ▲ ▲ ○ ○ ○ ▼ ○ ○ ○ ○ ▼ ○ ○ ▼ ○ ▼ ○ // ○ ○ ▲ ○ ○ ▲ ○ ○ ▲ ▲ ○ ○ ○ ▼ ○ ○ ○ ○ ▼ ○ ○ ▼ ○ ▼ ○
``` ```
@ -624,7 +624,7 @@ struct Person: Named, Aged {
var age: Int var age: Int
} }
func wishHappyBirthday(celebrator: protocol<Named, Aged>) { func wishHappyBirthday(celebrator: protocol<Named, Aged>) {
println("Happy birthday \(celebrator.name) - you're \(celebrator.age)!") print("Happy birthday \(celebrator.name) - you're \(celebrator.age)!")
} }
let birthdayPerson = Person(name: "Malcolm", age: 21) let birthdayPerson = Person(name: "Malcolm", age: 21)
wishHappyBirthday(birthdayPerson) wishHappyBirthday(birthdayPerson)
@ -642,9 +642,9 @@ wishHappyBirthday(birthdayPerson)
使用`is`和`as`操作符来检查协议的一致性或转化协议类型。检查和转化的语法和之前相同(*详情查看[Typy Casting章节](5)*): 使用`is`和`as`操作符来检查协议的一致性或转化协议类型。检查和转化的语法和之前相同(*详情查看[Typy Casting章节](5)*):
* `is`操作符用来检查实例是否`遵循`了某个`协议`。 * `is`操作符用来检查实例是否`遵循`了某个`协议`。
* `as?`返回一个可选值，当实例`遵循`协议时，返回该协议类型;否则返回`nil` * `as?`返回一个可选值，当实例`遵循`协议时，返回该协议类型;否则返回`nil`
* `as`用以强制向下转型。 * `as`用以强制向下转型。
```swift ```swift
@objc protocol HasArea { @objc protocol HasArea {
@ -697,9 +697,9 @@ let objects: [AnyObject] = [
```swift ```swift
for object in objects { for object in objects {
if let objectWithArea = object as? HasArea { if let objectWithArea = object as? HasArea {
println("Area is \(objectWithArea.area)") print("Area is \(objectWithArea.area)")
} else { } else {
println("Something that doesn't have an area") print("Something that doesn't have an area")
} }
} }
// Area is 12.5663708 // Area is 12.5663708
@ -754,7 +754,7 @@ for object in objects {
`count`属性用于存储当前的值，`increment`方法用来为`count`赋值。 `count`属性用于存储当前的值，`increment`方法用来为`count`赋值。
`increment`方法通过`可选链`，尝试从两种`可选成员`中获取`count`。 `increment`方法通过`可选链`，尝试从两种`可选成员`中获取`count`。
1. 由于`dataSource`可能为`nil`，因此在`dataSource`后边加上了`?`标记来表明只在`dataSource`非空时才去调用`incrementForCount`方法。 1. 由于`dataSource`可能为`nil`，因此在`dataSource`后边加上了`?`标记来表明只在`dataSource`非空时才去调用`incrementForCount`方法。
2. 即使`dataSource`存在，但是也无法保证其是否实现了`incrementForCount`方法，因此在`incrementForCount`方法后边也加有`?`标记 2. 即使`dataSource`存在，但是也无法保证其是否实现了`incrementForCount`方法，因此在`incrementForCount`方法后边也加有`?`标记
@ -776,7 +776,7 @@ var counter = Counter()
counter.dataSource = ThreeSource() counter.dataSource = ThreeSource()
for _ in 1...4 { for _ in 1...4 {
counter.increment() counter.increment()
println(counter.count) print(counter.count)
} }
// 3 // 3
// 6 // 6
@ -807,7 +807,7 @@ counter.count = -4
counter.dataSource = TowardsZeroSource() counter.dataSource = TowardsZeroSource()
for _ in 1...5 { for _ in 1...5 {
counter.increment() counter.increment()
println(counter.count) print(counter.count)
} }
// -3 // -3
// -2 // -2