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替换println 为 print

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chenyc
2015-07-21 17:35:04 +08:00
parent 0779f979ac
commit 1ffaef1bd5
16 changed files with 214 additions and 224 deletions
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57
source/chapter2/14_Initialization.md
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@@ -13,7 +13,7 @@
- [值类型的构造器代理](#initializer_delegation_for_value_types)
- [类的继承和构造过程](#class_inheritance_and_initialization)
- [可失败构造器](#failable_initializers)
- [必要构造器](#required_initializers)
- [必要构造器](#required_initializers)
- [通过闭包和函数来设置属性的默认值](#setting_a_default_property_value_with_a_closure_or_function)
@@ -39,7 +39,7 @@
```swift
init() {
// 在此处执行构造过程
// 在此处执行构造过程
}
```
@@ -53,7 +53,7 @@ struct Fahrenheit {
}
}
var f = Fahrenheit()
println("The default temperature is \(f.temperature)° Fahrenheit")
print("The default temperature is \(f.temperature)° Fahrenheit")
// 输出 "The default temperature is 32.0° Fahrenheit”
```
@@ -182,7 +182,7 @@ class SurveyQuestion {
self.text = text
}
func ask() {
println(text)
print(text)
}
}
let cheeseQuestion = SurveyQuestion(text: "Do you like cheese?")
@@ -210,7 +210,7 @@ class SurveyQuestion {
self.text = text
}
func ask() {
println(text)
print(text)
}
}
let beetsQuestion = SurveyQuestion(text: "How about beets?")
@@ -656,7 +656,7 @@ var breakfastList = [
breakfastList[0].name = "Orange juice"
breakfastList[0].purchased = true
for item in breakfastList {
println(item.description)
print(item.description)
}
// 1 x orange juice ✔
// 1 x bacon ✘
@@ -666,13 +666,13 @@ for item in breakfastList {
如上所述，例子中通过字面量方式创建了一个新数组`breakfastList`，它包含了三个新的`ShoppingListItem`实例，因此数组的类型也能自动推导为`ShoppingListItem[]`。在数组创建完之后，数组中第一个`ShoppingListItem`实例的名字从`[Unnamed]`修改为`Orange juice`，并标记为已购买。接下来通过遍历数组每个元素并打印它们的描述值，展示了所有项当前的默认状态都已按照预期完成了赋值。
<a name="failable_initializers"></a>
## 可失败构造器
## 可失败构造器
如果一个类，结构体或枚举类型的对象，在构造自身的过程中有可能失败，则为其定义一个可失败构造器，是非常有必要的。这里所指的“失败”是指，如给构造器传入无效的参数值，或缺少某种所需的外部资源，又或是不满足某种必要的条件等。
为了妥善处理这种构造过程中可能会失败的情况。你可以在一个类，结构体或是枚举类型的定义中，添加一个或多个可失败构造器。其语法为在`init`关键字后面加添问号`(init?)`。
> 注意：
> 注意：
可失败构造器的参数名和参数类型，不能与其它非可失败构造器的参数名，及其类型相同。
可失败构造器，在构建对象的过程中，创建一个其自身类型为可选类型的对象。你通过`return nil` 语句，来表明可失败构造器在何种情况下“失败”。
@@ -697,9 +697,9 @@ struct Animal {
```swift
let someCreature = Animal(species: "Giraffe")
// someCreature 的类型是 Animal? 而不是 Animal
if let giraffe = someCreature {
println("An animal was initialized with a species of \(giraffe.species)")
print("An animal was initialized with a species of \(giraffe.species)")
}
// 打印 "An animal was initialized with a species of Giraffe"
```
@@ -709,9 +709,9 @@ if let giraffe = someCreature {
```swift
let anonymousCreature = Animal(species: "")
// anonymousCreature 的类型是 Animal?, 而不是 Animal
if anonymousCreature == nil {
println("The anonymous creature could not be initialized")
print("The anonymous creature could not be initialized")
}
// 打印 "The anonymous creature could not be initialized"
```
@@ -748,13 +748,13 @@ enum TemperatureUnit {
```swift
let fahrenheitUnit = TemperatureUnit(symbol: "F")
if fahrenheitUnit != nil {
println("This is a defined temperature unit, so initialization succeeded.")
print("This is a defined temperature unit, so initialization succeeded.")
}
// 打印 "This is a defined temperature unit, so initialization succeeded."
let unknownUnit = TemperatureUnit(symbol: "X")
if unknownUnit == nil {
println("This is not a defined temperature unit, so initialization failed.")
print("This is not a defined temperature unit, so initialization failed.")
}
// 打印 "This is not a defined temperature unit, so initialization failed."
```
@@ -769,16 +769,16 @@ if unknownUnit == nil {
enum TemperatureUnit: Character {
case Kelvin = "K", Celsius = "C", Fahrenheit = "F"
}
let fahrenheitUnit = TemperatureUnit(rawValue: "F")
if fahrenheitUnit != nil {
println("This is a defined temperature unit, so initialization succeeded.")
print("This is a defined temperature unit, so initialization succeeded.")
}
// prints "This is a defined temperature unit, so initialization succeeded."
let unknownUnit = TemperatureUnit(rawValue: "X")
if unknownUnit == nil {
println("This is not a defined temperature unit, so initialization failed.")
print("This is not a defined temperature unit, so initialization failed.")
}
// prints "This is not a defined temperature unit, so initialization failed."
```
@@ -804,7 +804,7 @@ class Product {
```swift
if let bowTie = Product(name: "bow tie") {
// 不需要检查 bowTie.name == nil
println("The product's name is \(bowTie.name)")
print("The product's name is \(bowTie.name)")
}
// 打印 "The product's name is bow tie"
```
@@ -841,7 +841,7 @@ class CartItem: Product {
```swift
if let twoSocks = CartItem(name: "sock", quantity: 2) {
println("Item: \(twoSocks.name), quantity: \(twoSocks.quantity)")
print("Item: \(twoSocks.name), quantity: \(twoSocks.quantity)")
}
// 打印 "Item: sock, quantity: 2"
```
@@ -849,9 +849,9 @@ if let twoSocks = CartItem(name: "sock", quantity: 2) {
```swift
if let zeroShirts = CartItem(name: "shirt", quantity: 0) {
println("Item: \(zeroShirts.name), quantity: \(zeroShirts.quantity)")
print("Item: \(zeroShirts.name), quantity: \(zeroShirts.quantity)")
} else {
println("Unable to initialize zero shirts")
print("Unable to initialize zero shirts")
}
// 打印 "Unable to initialize zero shirts"
```
@@ -860,9 +860,9 @@ if let zeroShirts = CartItem(name: "shirt", quantity: 0) {
```swift
if let oneUnnamed = CartItem(name: "", quantity: 1) {
println("Item: \(oneUnnamed.name), quantity: \(oneUnnamed.quantity)")
print("Item: \(oneUnnamed.name), quantity: \(oneUnnamed.quantity)")
} else {
println("Unable to initialize one unnamed product")
print("Unable to initialize one unnamed product")
}
// 打印 "Unable to initialize one unnamed product"
```
@@ -920,7 +920,7 @@ class AutomaticallyNamedDocument: Document {
你也可以用 ```init？```重写 ```init！```，反之亦然。
你还可以用 ```init```代理调用```init！```，但这会触发一个断言：是否 ```init！```构造器会触发构造失败？
<a name="required_initializers"></a>
<a name="required_initializers"></a>
##必要构造器
在类的构造器前添加```required```修饰符表明所有该类的子类都必须实现该构造器：
@@ -1001,9 +1001,8 @@ struct Checkerboard {
```swift
let board = Checkerboard()
println(board.squareIsBlackAtRow(0, column: 1))
print(board.squareIsBlackAtRow(0, column: 1))
// 输出 "true"
println(board.squareIsBlackAtRow(9, column: 9))
print(board.squareIsBlackAtRow(9, column: 9))
// 输出 "false"
```