Swift语法快速索引

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我是靠谱客的博主危机钢笔，最近开发中收集的这篇文章主要介绍Swift语法快速索引，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

在WWDC的演示中就可以看出来Swift这个更接近于脚本的语言可以用更少的代码量完成和OC同样的功能。但是对于像我一样在战争中学习战争的同学们来说，天天抱着笨Swift Programming Language Reference之类的大部头看不实际。毕竟还是要养家糊口的。而且，那么1000+页内容讲的东西不是什么都要全部在平时工作中用到的。咱们就把平时用到的全部都放在一起，忘记了立马翻开看看，不知不觉的就学会了之后变成习惯。这样多省事。

变量

1 // Variable
2 var int_variable = 1
// 类型推断
3 var message : String
4 var x = 0.0, y = 0.0, z = 0.0

常量

// Constant
let const_int = 1
//const_int = 10
ERROR: can not assign to let value

字符串

// String
// 1. 定义
var empty_string = ""
var another_empty_string = String()
// 2. 拼接
var hello_string = "hello"
var world_string = " world"
hello_string += world_string
// hello world

let multiplier = 3
//let multiplier_message = "(mulitplier) times 2.5 is (Double(multiplier) * 2.5)"
// 3. 比较
var hello_world_string = "hello world"
hello_string == hello_world_string
// all are "hello world", result is true
if hello_string == hello_world_string {
println("These two are equal")
}

Tuple

// Tuple
// 1. Unnamed tuple
let http_not_found = (404, "Not Found")
println("tuple item 1 (http_not_found.0), tuple item 2 (http_not_found.1)")
// 2. Named tuple
let (statusCode, statusMessage) = (404, "Not Found")
statusCode
// 404
statusMessage
// "Not Found"

let http_not_found2 = (statusCode:404, statusMessage:"Not Found")
http_not_found2.statusCode
// 404
http_not_found2.statusMessage
// "Not Found"
// 3. return tuple
func getHttpStatus() -> (statusCode : Int, statusMessage : String){
// request http
return (404, "Not Found")
}

数组

// Array
// 1. 定义
//var empty_array = []
// 在swift里没事不要这样定义数组。这是NSArray类型的，一般是Array<T>类型的
var empty_array : [Int]
var empty_array2 = [Int]()
var fire_works = [String]()
var colors = ["red", "yellow"]
var fires : [String] = ["small fire", "big fire"]; // Xcode6 beta3里数组的类型是放在方括号里的
var red = colors[0]
// 2. append & insert
colors.append("black")
colors += "blue"
colors += fires
colors.insert("no color", atIndex: 0)
// 3. update
colors[2] = "light blue"
//colors[5...9] = ["pink", "orange", "gray", "limon"]
// 4. remove
colors.removeAtIndex(5)
//colors[0] = nil ERROR!
// other
colors.isEmpty
colors.count

字典

// Dictionary
// 1. 定义
var airports : Dictionary<String, String> = ["TYP":"Tokyo", "DUB":"Boublin"]
var airports2 = ["TYP":"Tokyo", "DUB":"Boublin"]
var empty_dic = Dictionary<String, String>()
var empty_dic2 = [:]
// 2. update
airports.updateValue("Dublin International", forKey: "DUB")
airports["DUB"] = "Dublin International"
// 3. insert
airports["CHN"] = "China International"
// 4. check exists
if let airportName = airports["DUB"] {
println("The name of the airport is (airportName).")
}
else{
println("That airport is not in the airports dictionary.")
}
// 5. iterate
for (airportCode, airportName) in airports{
println("(airportCode):(airportName)")
}
// 6. remove
airports.removeValueForKey("TYP")
airports["DUB"] = nil

枚举

// Enum
// 1. defination & usage
enum PowerStatus: Int{
case On = 1
case Off = 2
}
enum PowerStatus2: Int{
case On = 1, Off, Unknown
}
var status = PowerStatus.On
enum Barcode {
case UPCA(Int, Int, Int)
case QRCode(String)
}
var product_barcode = Barcode.UPCA(8, 8679_5449, 9)
product_barcode = .QRCode("ABCDEFGHIJKLMN")
switch product_barcode{
case .UPCA(let numberSystem, let identifier, let check):
println("UPC-A with value of (numberSystem), (identifier), (check)")
case .QRCode(let productCode):
println("QR code with value of (productCode)")
}

方法

// Function
// 1. 定义
func yourFuncName(){
}
// 2. 返回值
func yourFuncNameWithReturnType()->String{
return ""
}
// 3. 参数
func funcWithParameter(parameter1:String, parameter2:String)->String{
return parameter1 + parameter2
}
funcWithParameter("1", "2")
// 4. 外部参数名
func funcWithExternalParameter(externalParameter p1:String) -> String{
return p1 + " " + p1
}
funcWithExternalParameter(externalParameter: "hello world")
func joinString(string s1: String, toString s2: String, withJoiner joiner: String)
-> String {
return s1 + joiner + s2
}
joinString(string: "hello", toString: "world", withJoiner: "&")
// 外部内部参数同名
func containsCharacter(#string: String, #characterToFind: Character) -> Bool {
for character in string {
if character == characterToFind {
return true
}
}
return false
}
containsCharacter(string: "aardvark", characterToFind: "v")
// 默认参数值
func joinStringWithDefaultValue(string s1: String, toString s2: String, withJoiner joiner: String = " ")
-> String {
return s1 + joiner + s2
}
joinStringWithDefaultValue(string: "hello", toString: "world") //joiner的值默认为“ ”
// inout参数
func swapTwoInts(inout a: Int, inout b: Int) {
let temporaryA = a
a = b
b = temporaryA
}
var someInt = 3
var anotherInt = 107
swapTwoInts(&someInt, &anotherInt)
println("someInt is now (someInt), and anotherInt is now (anotherInt)")
// prints "someInt is now 107, and anotherInt is now 3

类

// Class
// 1. 定义
class NamedShape {
var numberOfSides: Int = 0
var name: String


// *这样定义的初始化函数，其参数在调用的时候必须作为外名称使用
init(name: String) {
self.name = name
}


// *这样定义的参数，在初始化的时候可以不使用外名称

init(_ nickName: String){

self.name = nickName

}

func simpleDescription() -> String {
return "A shape with (numberOfSides) sides."
}
}

// 2. 继承 & 函数重载 & 属性getter setter
class Square: NamedShape {
var sideLength: Double
init(sideLength: Double, name: String) {
self.sideLength = sideLength
super.init(name: name)
numberOfSides = 4
}
func area() ->
Double {
return sideLength * sideLength
}
// 函数重载
override func simpleDescription() -> String {
return "A square with sides of length (sideLength)."
}
}
class EquilateralTriangle: NamedShape {
var sideLength: Double = 0.0
init(sideLength: Double, name: String) {
self.sideLength = sideLength
super.init(name: name)
numberOfSides = 3
}
// 属性的getter setter
var perimeter: Double {
get {
return 3.0 * sideLength
}
set {
sideLength = newValue / 3.0
}
}
override func simpleDescription() -> String {
return "An equilateral triagle with sides of length (sideLength)."
}
}
// 3. 使用
var triangle = EquilateralTriangle(sideLength: 3.1, name: "a triangle")
triangle.perimeter
triangle.perimeter = 9.9
triangle.sideLength

使用闭包给属性赋初值

struct Checkerboard {
let boardColors: Bool[] = {
var temporaryBoard = Bool[]()
var isBlack = false
for i in 1...10 {
for j in 1...10 {
temporaryBoard.append(isBlack)
isBlack = !isBlack
}
isBlack = !isBlack
}
return temporaryBoard
}()
func squareIsBlackAtRow(row: Int, column: Int) -> Bool {
return boardColors[(row * 10) + column]
}
}

类（二）

1. 属性的初始化

2. init函数中修改常量属性

struct Color{
// 在初始化函数中可以修改这些在定义时没有给出初始值的属性

let red, green, blue: Double
// stored property（就是下面这样定义的），如果是optional的（结尾时？活着！），可以在初始化函数
// 中不给出初始值，否则必须给出初始值。
var alpha: Double!
init(r red: Double, green: Double, blue: Double){
self.red = red
self.green = green
self.blue = blue
}
init(white: Double){
red = white
green = white
blue = white
}
init(_ aColor: Double){
self.red = aColor
self.green = aColor
self.blue = aColor
}
}

3. 构造函数

// 默认init函数
class ShoppingItem {
var name: String?
//
var quantity: Int // 编译错误，要使代码正确需要注释掉这一句
var purchased = false
// 除非定义的属性全部都有初始值。optional的属性的默认值是nil。
// 否则的话必须显示定义一个init函数。

init(){
}
init(name: String, purchased: Bool){
self.name = name
self.purchased = purchased
}
// 结构体等自定义值类型可以直接在一个init函数中使用self.init(...)的方式调用
// 其他的init函数。但是在class（引用类型）中需要显示制定convenience关键字
// 才可以调用其他的init函数

convenience init(name: String){
self.init(name: "hello", purchased: true)
}
}
var item = ShoppingItem()
struct Color{
// 在初始化函数中可以修改这些在定义时没有给出初始值的属性

let red, green, blue: Double
// stored property（就是下面这样定义的），如果是optional的（结尾时？活着！），可以在初始化函数
// 中不给出初始值，否则必须给出初始值。
var alpha: Double!
init(r red: Double, green: Double, blue: Double){
self.red = red
self.green = green
self.blue = blue
}
//在init函数中调用其他init函数

init(white: Double){
//
red = white
//
green = white
//
blue = white
self.init(r: 1.0, green: 2.0, blue:1.0)
}
}

convenience的init函数只能在本类中调用。而一般的init函数（也就是designated init）可以在继承的链中在一个类中调用super类的init函数。

继承

不想什么被继承就在什么的前面放个final关键字（以前有@号，现在木有了）。如果在class前面放final关键字的话，那么整个类不可以被继承。

class ShoppingListItem: ShoppingItem{
final var wishListed: Bool? // 不被继承
override init(){
super.init(name: "what", purchased: false)
}
}

析构函数

class Vehicle{
var numberOfWheels = 0
var description: String{
return "(numberOfWheels) wheel(s)"
}
deinit{
// 析构具体内容

}
}

析构函数执行的特点：

1. 系统自动调用，不允许手动调用

2. 执行完本类调执行super类的

3. 执行完析构函数之后实例才释放，所以可以析构函数里可以访问全部属性的值

WEAK 和 UNOWNED关键字

class Customer{
let name: String
var card: CreditCard?
init(name: String) {
self.name = name
}
}
class CreditCard{
let number: Int
/*
* weak和owned关键字都用来修饰属性的，为了防止循环引用造成的内存无法释放。
* 区别就在于unowned是一定要有值的。所以unowned只可以用在非可选类型上（non-optional type）
*/
unowned let customer: Customer
init(number: Int, customer: Customer){
self.number = number
self.customer = customer
}
}

在闭包中也会出现这样的问题。如果在闭包中使用了self.xxxProperty也会出现对类实例本身的一个强引用，从而出现了循环引用。PS：在闭包中使用类成员的时候必须要用self.的写法。


}
}
class HTMLElement {
let name: String
let text: String?
lazy var asHTML: () -> String = {
[unowned self] in
if let text = self.text {
return "<(self.name)>(text)</(self.name)>"
} else {
return "<(self.name) />"
}
}
init(name: String, text: String? = nil) {
self.name = name
self.text = text
}
deinit {
println("(name) is being deinitialized")
}
}