/*字符串*/
    //初始化
    var emptyString = "" // 空字符串字面量
    var anotherEmptyString = String() // 初始化方法
    // 兩個字符串均為空并等價厅缺。
    //判斷該字符串是否為空
    if emptyString.isEmpty {
        print("Nothing to see here")
    }
    
    
    //字符串的可變性
    var variableString = "Horse"
    variableString += " and carriage"
    
    //let constantString = "Highlander"
    //constantString += " and another Highlander"
    // 這會報告一個編譯錯誤 (compile-time error) - 常量字符串不可以被修改。
    
    
    //使用字符串
    
    //通過for in 循環(huán)來遍歷字符串中的每一個字符的值
    for character in "Dog!?".characters {
        print(character)
    }
    
    //通過標(biāo)明一個Character類型并用字符字面量進(jìn)行賦值，可以建立一個獨立的字符串常量或變量：
    let exclamationMark:Character = "!"
    let carCharacters:[Character] = ["C", "a", "t", "!", "?"]
    let catString = String(carCharacters)
    print(catString)
    
    //鏈接字符串和字符渔工，可以用 + 號拼接字符串
    let string1 = "Hello"
    let string2 = " there"
    var welcome = string1 + string2
    //可以用+=將一個字符串添加到一個已經(jīng)存在的字符串變量上
    var instruction = "look over"
    instruction += string2
    
    //可以用append()方法將一個字符附加到字符串變量的尾部
    welcome.append(exclamationMark)
    
    //字符串插入
    //字符串插值是一種構(gòu)建新字符串的方式,可以在其中包含常量的诵、變量碉钠、字面量和表達(dá)式驳糯。 您插入的字符串字面量 的每一項都在以反斜線為前綴的圓括號中:
    
    let multiplier = 3
    let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)" // message 是 "3 times 2.5 is 7.5"
    
    
    //Unicode
    
    //Unicode是一個國際標(biāo)準(zhǔn)吼鳞，用于文本的編碼和表示，可以用標(biāo)準(zhǔn)格式表示任意語言蔼两。并能夠?qū)ξ谋疚募蛘呔W(wǎng)頁這樣的外部資源中的字符串進(jìn)行讀寫操作甩鳄，swift的string和Character類型是完全兼容Unicode標(biāo)準(zhǔn)的
    
    //計算字符數(shù)量
    let  unusualMenagerie = "Koala ?, Snail ?, Penguin ?,Dromedary ?"
    print("unusualMenagerie has \(unusualMenagerie.characters.count) characters")
    
    
    //訪問和修改字符串
    //字符串的索引
    let greeting = "Guten Tag!"
    greeting[greeting.startIndex]
    greeting[greeting.index(before: greeting.endIndex)]
    greeting[greeting.index(after:greeting.startIndex)]
    let index  =  greeting.index(greeting.startIndex,offsetBy: 7)
    
    
    //插入和刪除
    var welcome2 = "Hello"
    welcome2.insert("!", at: welcome2.endIndex)//在最后插入!
    welcome2.insert(contentsOf:" there".characters, at: welcome2.index(before: welcome2.endIndex))
    print(welcome2)
    
    //刪除
    welcome2.remove(at: welcome2.index(before: welcome2.endIndex))
    
    let  range = welcome2.index(welcome2.endIndex, offsetBy: -8)..<welcome2.endIndex
    welcome2.removeSubrange(range)
    print(welcome2)
    
    //比較字符串
    var string = "XuBaoAiChiYu_QQ_1045214799"
    let compareStr = "XuBaoAiChiYu_QQ_1045214799"
    let searchRange = string.characters.index(string.startIndex, offsetBy: 5)..<string.characters.index(before: string.endIndex)
    print(searchRange)
    
    //前綴
    var isHas = string.hasPrefix("Xu")
    print("hasPrefix:\(isHas)")
    
    //后綴
    isHas = string.hasSuffix("1045214799")
    print("hasSuffix:\(isHas)")
    
    //全比較是否相同
    isHas = string == compareStr
    print(isHas)
    
    //比較大小
    var result = string.compare(compareStr)
    print(result.hashValue)
    
    //添加比較范圍
    result = string.compare(compareStr, options: NSString.CompareOptions.caseInsensitive, range: searchRange, locale: nil)
    print("result:\(result.hashValue)")
    
    // 返回兩個字符串相同的前綴
    string = string.commonPrefix(with: compareStr, options: NSString.CompareOptions.caseInsensitive)
    print(string)

//字符串轉(zhuǎn)int類型
 var atr:String = "12345"
    func stringToInt(atr:String) -> NSInteger {
        let string = atr
        var int: Int?
        if let doubleValue = Int(string) {
            int = Int(doubleValue)
        }
        if int == nil
        {
            return 0
        }
        return int!
        
    }t

    var intNum:NSInteger = stringToInt(atr: atr)
    
    print(intNum)

1.CGFloat 轉(zhuǎn)化成String

let strs:String = String.init(format: "%.2f", order.fare!)
2.String 轉(zhuǎn)化成CGFloat
func StringToFloat(str:String)->(CGFloat){

    let string = str
    var cgFloat: CGFloat = 0
    

    if let doubleValue = Double(string)
    {
        cgFloat = CGFloat(doubleValue)
    }
    return cgFloat
}