1.Swift 基础语法

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变量

var

// 变量var a = 6;var b = 26;

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常量

let

// 常量let c = a+b;

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指定变量类型

:String :Int ……

// 指明变量类型var s = "Save"var y:String = "you"var z:Int = 6 ;

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print

print

Swift2.0后，就废弃和原有的println方法，同时拓展的print方法。
那么用
print换行

print("pirntln!", terminator: "\n")

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字符串拼接

"\()"

// 字符串连接var s2 = "Save"var s3 = "you"var i = 06s3 = "\(s2) \(s3)"var s4 = "\(s3) \(i)"print(s4, terminator: "\n")

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数组

// 数组var array = ["Save","you",0,6]var array2 = []var array3 = [String]()print(array, terminator: "\n")print("[] = \(array2)", terminator: "\n")print("[String]() = \(array3)", terminator: "\n")

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字典

var dict = ["name":"CaMnter","age":"22"]dict["language"] = "Swift"print(dict, terminator: "\n")print(dict["language"], terminator: "\n")

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循环

for

var dict = ["name":"CaMnter","age":"22"]for (key,value) in dict{    print("\(key) \(value)", terminator: "\n")}for index in 0...5{    print(index, terminator: "\n")}var i1 = 5while i1<10{    print(i1, terminator: "\n")    i1++}

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? 和 ！

var s:String?var s:String!

?的作用
- 1.声明Optional值变量
- 2.对Optional值操作中，用来判断是否能响应后面的操作
- 3.安全调用protocol的optional方法
- 4.as? 向下转型(Downcast)

!的作用
- 1.强制对Optional值进行拆包(unwrap)
- 2.声明Implicitly Unwrapped Optionals值，一般用于类中的属性

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流程控制

if 和if let

for index2 in 0...10{    if index2%2 == 0{        print(index2, terminator: "\n")    }}

有一种独特的流程控制是if let，可用于判断变量或者表达式的值是否为空。 s7这里就相当于一个Optional类型，用于判断下面的操作是否执行。

var s5:String?="CaMnter"var s6:String?="\n"s6 = nilif let s7=s5{    print(s5, terminator: "\n")}if let s8=s6{    print(s6, terminator: "\n")}

只输出结果为s6的值，因为s5赋值给s7后，判断了s7为nil，下面括号里的操作就不执行了。

Optional("CaMnter")

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函数

// 无返回值func say(name:String){    print("\(name)", terminator: "\n")}// 有返回值(返回多个)func getValue()->(String,String){    return ("CaMnter","Swift")}// 接收多个返回值let (s9,s10) = getValue()print(s10, terminator: "\n")// 可以定义一个变量接收函数var fun1 = saysay("Save you from anything")

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类 和 继承

class 和 :

// 父类class Parent {    func info(){        print("Parent class", terminator: "\n")    }}// 继承自父类class Child: Parent {    var _tag:String    init(tag:String) {        self._tag=tag    }    // 重写父类的方法    override func info() {        print("Child class \(self._tag)", terminator: "\n")    }}var p = Parent()var c2 = Child(tag: "CaMnter")p.info()c2.info()

输出结果：

Parent classChild class CaMnter