Swift国内社区: SwiftMic
Swift 是一门多用途的程序语言，它使用现代的方法来实现安全性、高性能和多样的软件设计模式。
本文主要简单地介绍下 Swift 的基本语法。
Swift Version: Xcode 7.3.1 Default
- 导入 package
import Foundation
import UIKit
- 变量和常量
var str1 = "Hello, playground"
let str2 = "test"
- 数组
var myArray = [
"t1",
"t2",
"t3"
]
- 集合
let ttt: Set = [0, 1, 2, 3, 6, 9, 90, 2]
- 字典
var myDict = [
"k1": "v1",
"k2": "v2",
"k3": "v3"
]
- 方法
func test(value: Int) -> Bool {
if(value > 10) {
return true
}
// 编译错误，Swift强制if语句加{}
// if(value > 10)
// return true
return false
}
- 多重返回值函数
func test1(value: Int) -> (errorCode: Int, errorDes: String) {
if(value > 10) {
return (200, "Success")
}
return (404, "Not Found")
}
let r = test(100)
let r1 = test1(90)
print("result1 = (\(r1.0), \(r1.1))")
print("result1 = (\(r1.errorCode), \(r1.errorDes))")
- 区间运算符
// 闭区间运算符（a...b）定义一个包含从a到b(包括a和b)的所有值的区间，b必须大于a。
for index in 1...5 {
print("index = \(index)")
}
// 半开区间运算符
for index in 1..<5 {
print("index = \(index)")
}
- 闭包
let names = ["Chris", "Alex", "Ewa", "Barry", "Daniella"]
func backwards(s1: String, s2: String) -> Bool {
return s1 > s2
}
func closureTest(param1: Int, param2: (s1: String, s2: String) -> Bool) {
print("param1 = \(param1), param2 = \(param2(s1: "d", s2: "b"))")
}
closureTest(1, param2: backwards)
closureTest(2, param2: {
(s1: String, s2: String) -> Bool in
return s1 < s2
})
closureTest(3, param2: {
(s1, s2) in // 类型可自动推倒出来
return s1 < s2
})
closureTest(4, param2: {(s1, s2) in return s1 < s2})
closureTest(5, param2: {$0 > $1})
// 运算符函数
closureTest(6, param2: >)
- 尾随闭包
func trailingClosuresTest(param: () -> ()) {
print("trailingClosuresTest 1")
param()
print("trailingClosuresTest 2")
}
// 以下是不使用尾随闭包进行函数调用
trailingClosuresTest({
() -> () in
print("trailingClosuresTest 3")
})
trailingClosuresTest({
print("trailingClosuresTest 4")
})
// 以下是使用尾随闭包进行函数调用
trailingClosuresTest() {
print("trailingClosuresTest 5")
}
// 如果函数只需要闭包表达式一个参数，当使用尾随闭包时，甚至可以把()省略掉。
trailingClosuresTest {
print("trailingClosuresTest 6")
}
- 捕获值
func makeIncrementor(forIncrement amount: Int) -> () -> Int {
var runningTotal = 1
func incrementor() -> Int {
runningTotal += amount
return runningTotal
}
return incrementor
}
let capture1 = makeIncrementor(forIncrement: 9)
print(capture1())
print(capture1())
print 输出如下：
10
19
- 枚举
enum Barcode {
case UPCA(Int, Int, Int)
case QRCode(String)
}
func enumTest(value: Barcode) {
switch(value) {
case Barcode.UPCA(let numberSystem, let identifier, let check):
print("UPCA numberSystem = \(numberSystem), identifier = \(identifier), check = \(check)")
case Barcode.QRCode(let productCode):
print("QRCode productCode = \(productCode)")
}
}
enumTest(Barcode.QRCode("qs"))
enumTest(Barcode.UPCA(1, 2, 3))
enum Planet: Int {
case Mercury = 1, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
}
enum StrEnum : String {
case T1 = "a"
case T2 = "b"
}
- 计算属性
struct Point {
var x = 0.0
var y = 0.0
}
struct Size {
var width = 0.0
var height = 0.0
}
struct Rect {
var origin = Point()
var size = Size()
var center: Point {
get {
let centerX = origin.x + (size.width / 2.0)
let centerY = origin.y + (size.height / 2.0)
return Point(x: centerX, y: centerY)
}
set {
origin.x = newValue.x - (size.width / 2.0)
origin.y = newValue.y - (size.height / 2.0)
}
}
}
var square = Rect(origin: Point(x: 0.0, y: 0.0), size: Size(width: 10.0, height: 10.0))
print("square.center = \(square.center)")
square.center = Point(x: 15.0, y: 15.0)
print("square origin = \(square.origin)")
print 输出如下：
square.center = Point(x: 5.0, y: 5.0)
square origin = Point(x: 10.0, y: 10.0)
- 属性观察器
class StepCounter {
var totalSteps: Int = 0 {
willSet(newTotalSteps) {
print("1 totalSteps = \(totalSteps)")
}
didSet {
if(totalSteps > oldValue) {
print("2 totalSteps = \(totalSteps)")
}
}
}
}
let stepCounter = StepCounter()
stepCounter.totalSteps = 100
print 输出如下：
1 totalSteps = 0
2 totalSteps = 100
- 结构体
struct PointTest {
var x = 0.0
var y = 0.0
mutating func moveBy(deltaX: Double, deltaY: Double) {
x += deltaX
y += deltaY
}
}
使用 mutating 关键字是为了能在该方法中修改 struct 的变量。
- 构造、析构、! 、?
class Player {
init() {
print("Player init")
}
deinit {
print("Player deinit")
}
func test() {
}
}
var player: Player? = Player() // 调用构造方法
if(nil != player) {
player!.test()
}
// 等价于上面这种情况
player?.test()
player = nil // 调用析构方法
- 继承 － 单继承，多实现
class A {
}
class B : A {
}
protocol IA {
}
protocol IB {
}
protocol IC {
}
class C : A, IA, IB, IC {
}
- extension
extension Double {
var km: Double { return self * 1_000.0 }
var m : Double { return self }
var cm: Double { return self / 100.0 }
var mm: Double { return self / 1_000.0 }
var ft: Double { return self / 3.28084 }
}
let t = 45.7.km
print(t)
print 输出如下：
45700.0