Swift3.0-数据类型

学无止境 keep moving

定义基本数据格式

    let myKobe = 24
    
    let myData : Double = 23.0  //指定类型定义
     
    let binaryInteger = 0b10001 //二进制数
    
    let octalInteger = 0o21     //八进制数
    
    let hexadecimalInteger = 0x11 //十六进制
    
    let scienceNumber = 1.234e3 //科学计数

变量定义

var myVariable =  23

类型转换

        var leb  = "23"
        let str = "\(leb)"
        let str1 = String(str)
        let str2 = Int(str)
        let str3 = Int(leb)
        let str4 = Double(str1!)

数组的定义方式

        let list1 = ["bonjour","23","3"]
        var list2 : [String] = ["bonjour","23","3"]
        let list3 : [Any] = ["bonjour","33","4"]
        let list4 : NSArray = ["bonjour","23","1"]
        let list5 :NSMutableArray = ["bonjour","423","4"]
        //remove
        list2.removeAll()  //var 可以
        list2 = []  //var 可以
        
        list5.removeAllObjects() // var 和 let 都可以

        tempArray[1...4] = ["沙扬娜拉","apple"] // 将数组4...6 的范围用指定的数组取代
        list5.add("34")
        list5.insert("Maple Syrup", at: 0)
        list5.removeObject(at: 1)

字典的定义方式

        let dict1 : [String : Int] = [:]
        let dict2 = [String:Int]()
        let dict3 : NSDictionary = NSDictionary()
        let dict4 : NSMutableDictionary  = NSMutableDictionary()

获取数据类型的最大和最小值

        let minValue = UInt8.min
        let maxValue = UInt8.max

给数据类型设置别名

        typealias code = Int32
        var tel : code = 35232

元祖

1.定义

        //第一种定义方式
        let http404Error = (404,"Not Found")
        
        let codeNum = http404Error.0
        
        let error = http404Error.1
        
        //第二种定义方式
        
        let http404Error = (code:404, error:"Not Found")
        
        let codeNum = http404Error.code
        
        let error = http404Error.error
        
        //第三种定义方法
        let http404Error:(code:Int,error:String) = (404,"Not Found")
        
        let code = http404Error.code
        
        let error = http404Error.1
        
        //第四种定义方法
        
        let http404Error:(code:Int,error:String) = (code:404,error:"Not Found")
        
        let code = http404Error.code
        
        let error = http404Error.error
        
        //第五种定义方式
        
        var http404Error :(code:Int , error : String) = (_ :404, _ : "Not Found")

//第四种定义的时候,等号坐标和右边的元素名称必须对应,不然系统会报错,建议不使用这种方式定义

2.分解变量

        let (statusCode, _) = http404Error //缺省不需要的值
        let (statusCode, statusMessage) = http404Error

3. 赋值

        var http404Error : (code:Int,error:String)
        http404Error = (code:404,error:"Not Found")//完整
        http404Error = (404, "Not Found") //全部名称缺省
        http404Error = (code : 404, "Not Found") //部分缺省
        http404Error = (_ :404 , "Not Found")

字符串

        let string = "Hello." + "World" //so Fantice let
        
        var name = "natali"
        name.append("你好") // var 
        
        var anotherEmptyString = String()
        
        //判断字符串是否为空
        var emptyString = String()
        if emptyString.isEmpty {
            print("Nothing to see here")
        }
        
        //获取字符串中每个字符
        for character in "Dog!🐶".characters {
            print(character)
        }
        
        let nike = "Nothing is impossiable"
        for indedx in nike.characters.indices {
            print("\(nike[indedx])", separator: "1", terminator: "")
        }
        
        //定义字符
        let exclamationMark :(Character) = "!"
        //定义字符数组
        let carcharacters : [Character] = ["C", "a", "t", "!", "🐱"]
        //定义数组转字符串
        let catString = String(carcharacters)
        //Unicode编码
        let percomosed:Character = "\u{D55C}"                //🇰🇷
        let regionalIndicatorForUS: Character = "\u{1F1FA}\u{1F1F8}" //🇺🇸
        
        var nickname = "🐶东西add"
        print(nickname.characters.count) // 6 都是一个字符
        
        //截取字符串
        let greeting = "bonjunor"
        //截取单个
        greeting[greeting.startIndex]
        //截取一段
        greeting[greeting.index(greeting.startIndex, offsetBy: 2)..<greeting.index(greeting.endIndex, offsetBy: -3)]
        //在指定位置插入字符串
        var welcome = "welcome"
        welcome.insert("!", at: welcome.endIndex)
        welcome.insert(contentsOf: "here".characters, at: welcome.index(before: welcome.endIndex))
        
        //移除字符串
//        welcome.remove(at: welcome.index(before: welcome.endIndex))

        let range = welcome.index(welcome.endIndex, offsetBy: -6)..<welcome.endIndex

        welcome.removeSubrange(range)
        
        // 前缀和后缀
        
        let scene = "Capulet`s mansion"
        
        if scene.hasSuffix("Capulet`s mansion") {
            
        } //hasPrefix
        
        //获取对应的编码数据
        for codeunit in "🐶a店待你".utf16 {
            print("\(codeunit)")
        }

深入学习

拓展

extension Int {
    func description() -> String {
        return "这是一个Int类型的数\(self)"
    }
}

        print(2.description())

这是一个Int类型的数2

1.定义一个协议

protocol NumberProtocl {
    
    func description() -> String
    
}

2.拓展实现协议

extension Int : NumberProtocl {
    
    func description() -> String {
        return "This is a Int Number\(self)"
    }
    
}

extension Double : NumberProtocl {
    
    func description() -> String {
        return "This is a Double Number \(self)"
    }
    
}

3.定义一个协议类型

        var a:NumberProtocl = 3
        print(a.description())
        a = 3.4
        print(a.description())

运行

我是一个Int类型的数字3
我是一个Double类型的数字3.4

通过这种方法,我们可以给同一个变量,赋值不同类型的值了,其实这个符合swift的语法要求,只是我们利用它的灵活性,达到了我们的目的

给系统类添加拓展

给Int 类型和 Double类型增加一个方法,判断它的数据类型

//定义一个协议
protocol whichTypeProtocol {
    
}

//拓展实现协议
extension Int : whichTypeProtocol{
    
}

extension Double : whichTypeProtocol {
    
}

//给协议拓展方法
extension whichTypeProtocol {
    func description() -> String {
        if self is Int {
            return " This is Int \(self)"
        }
        if self is Double {
            return "This is Double \(self)"
        }
        
        return "Nothing"
    }
}

print(3.44.description())
print(3.description())

Self的好处

专门用于不确定数据类型的

需求:给所有数字类型,扩展一个平方的函数,返回自己的操作

//定义一个协议
protocol getSpuareValue {
}

//拓展实现协议
extension Int : getSpuareValue {
    
}

extension Double : getSpuareValue {
    
}

extension getSpuareValue {
    
    //我们不确定返回的self 是什么类型
    func spuareValue() -> Self {
        if self is Int {
            let n = self as! Int
            return n * n as! Self
        }
        if self is Double {
            let m = self as! Int
            return m * m as! Self
        }
        return 0 as! Self
    }
    
}
print(3.44.squareValue())
print(3.squareValue())

11.8336
9

结论
Self很强大

需要注意的地方

1.如果指出变量的类型,赋值的值必须是和他类型相同的值,不然编译不通过

var num:Int = 43.0//(编译错误)

2.浮点数类型推断出来的默认为Double类型

let name = 30.0 // Double

3.Float 类型的值 赋值给Double类型也必须转换

let name:Float = 30.0
let explicitDouble: Double = Double(name)

4.数字之间的转换结果为非可选值,数字转字符串也是非可选值,但是字符串转数字就是可选值(因为它有可能转换失败)

let str = "\(num1)"
let str1 = String(num1)
let num2 = Int(num1)
let num3 = Int(str1)
let num4 = Double(str1)

输出结果:

30.0
30
nil
Optional(30.0)

注意:

字符串33.0 转Int 类型只会是nil 不会是33 因为字符串33.0 不是Int类型转换失败,但是浮点数33.0 可以转换为33

5.不能推断出下面的类型

let list1 = ["你好","2","3",3] // 不能这样写,swift推断不出来

你应该:

let list1 = ["你好","2","3",3] as [Any]
let list1:[Any] = ["你好","2","3",3]
let list1:NSArray = ["你好","2","3",3]
let list1:NSMutableArray = ["你好","2","3",3]

6.使用Dictionary定义字典必须指定数据类型

let dic5:Dictionary = [:] // 错误
let dic5:Dictionary = [String:Int]() // 正确

Array 和NSArray,NSMutableArray的区别
1.测试类型

var list1:Array = ["你好","2","3","4"]
let list2 = list1
list1[1] = "哈哈"
print(list1)
print(list2)

运行结果:

["你好", "哈哈", "3", "4"]
["你好", "2", "3", "4"]

var list1:NSMutableArray = ["你好","2","3","4"]
let list2 = list1

list1[1]="哈哈"
print(list1)
print(list2)

运行结果:

("你好", "哈哈", "3", "4")
("你好", "哈哈", "3", "4")

结论:

Array 为值类型,NSArray,NSMutableArray为引用类型

2.测试内存占用

func add(){
    var array: [Any] = [3]
    for _ in 0...10000000{
        array.append(3)
    }
}

执行代码前 3.5M 执行代码后 3.8 M 内存占用最高 308.6M

func add(){
    let array: NSMutableArray = NSMutableArray()
    for i in 0...10000000{
        array.add(3)
        if i == 10000000{

        }

    }
}

执行代码前3.5 M ,代码执行完毕后 17.3M,内存占用最高为 422.3

3.我们使用Array 放对象

func add(){
    var array: [Any] = []
    for i in 0...10000{
        array.append([UILabel()])
    }
运行前 3.5 运行后10.5 最高占内存 21.5，发现内存没有释放完毕

尝试修改代码如下:

autoreleasepool {
        var array: [Any] = []
        for i in 0...10000{
            array.append([UILabel()])
        }
    }

运行结果依旧
结论:

Swift 中新增的Array 存放非对象类型,内存清理的更及时,更彻底!

4.数据的上溢或者下溢系统都会报错

Int8.min - 1
Int8.max + 1

arithmetic operation '127 + 1' (on type 'Int8') results in an overflow
error: arithmetic operation '-128 - 1' (on type 'Int8') results in an overflow

原文出处
作者：酷走天涯
链接：http://www.jianshu.com/p/a53429e4e2f3