swift 语法总结

//输出

println("Hello, world”)

//var定义变量  let定义常量

var myVariable = 42

myVariable = 50

let myConstant = 42

//定义常量或变量的时候指定类型

let implicitInteger = 70

let implicitDouble = 70.0

let explicitDouble: Double = 70

//定义字符串

let label = "The width is “

let width = 94

let widthLabel = label + String(width)

//在字符串中添加值

let apples = 3

let oranges = 5

let appleSummary = "I have \(apples) apples”

let fruitSummary = “I have \(apples + oranges) pieces of fruit.”

//创建字典和数组

var shoppingList = ["catfish","water", "tulips","blue paint”]

shoppingList[1] = "bottle of water”

var occupations = [

     "Malcolm": "Captain”,

     "Kaylee": "Mechanic”,

     ]

occupations["Jayne”] = "Public Relations”

//创建空数组和空字典

let emptyArray = String[]()

let emptyDictionary = Dictionary<String, Float>()

//for in 语句

let individualScores = [75, 43, 103, 87, 12]

for index in individualScores {

    println("\(index) times 5 is \(index * 5)")

}

let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]

for (animalName, legCount) in numberOfLegs {

    println("\(animalName)s have \(legCount) legs")

}

for character in "Hello" {

    println(character)

}

//for循环

for var index = 0; index < 3; ++index {

    println("index is \(index)")

}

//while

var square = 0

var diceRoll = 0

while square < finalSquare {

    // roll the dice

    if ++diceRoll == 7 { diceRoll = 1 }

    // move by the rolled amount

    square += diceRoll

    if square < board.count {

        // if we're still on the board, move up or down for a snake or a ladder

        square += board[square]

    }

}

println("Game over!")

//if else

temperatureInFahrenheit = 90

if temperatureInFahrenheit <= 32 {

    println("It's very cold. Consider wearing a scarf.")

} else if temperatureInFahrenheit >= 86 {

    println("It's really warm. Don't forget to wear sunscreen.")

} else {

    println("It's not that cold. Wear a t-shirt.")

}

//switch case

64

//问号 感叹号

！告诉编译器这个变量绝对不为nil，当为nil的时候会报错

？告诉编译器这个变量可能为nil，当为nil的时候不会报错

//创建单例

import UIKit

 

classDataCenter: NSObject {

 

    classlet dataCenterObj:DataCenter = DataCenter()

 

    classfunc getDataCenter() ->DataCenter {

        returndataCenterObj

    }

}

6.协议（Protocols）

语法:

在Objective-C中我们这么声明Protocol:

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@protocol SampleProtocol

- (void)someMethod;

@end

而在Swift中：

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protocol SampleProtocol 

{

    func someMethod()

}

在Swift遵循协议:

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class AnotherClass: SomeSuperClass, SampleProtocol

{

    func someMethod() {}

}

那么之前Objective-C的protocol中,我们可以标志optional。那在Swift中呢？

遗憾的是,目前纯Swift的protocol还不支持optional。但根据苹果官方论坛的一位员工的回答,未来Swift是会支持的。