Swift String

字符串的子串

// MARK:字符串的子串
    func demo4() {
        //建议：一般使用NSString作为中转，因为swift取字串方法一直在优化
        let str = "我们一起去飞"
        let ocStr = str as NSString
        let s1 = ocStr.substring(with: NSMakeRange(2, 3))
        print(s1)
        
        print(str.startIndex)
        print(str.endIndex)
 
        
        guard let range=str.range(of: "一起") else {
            print("没有找到字符串")
            return
        }
        print(range)
        
    }

格式化

// MARK:格式化
func demo3() {
    let h = 8
    let m = 9
    let s = 6
    
    let dateStr = "\(h):\(m):\(s)"
    print(dateStr)
    //使用格式字符串格式化
    let dateStr1 = String(format: "%02d:%02d:%02d", h,m,s)
    print(dateStr1)
    
}

字符串的拼接

// MARK:字符串拼接
func demo2() {
    let str1 = "hello "
    let str2 = "word"
    var str = ""
    str = str1 + str2
    
    let name = "老王"
    let age = 18
    let title:String? = "BOSS"
    let point = CGPoint(x: 100, y: 200)
    
    // \(变量/常量)
    let str1 = "\(name) \(age) \(title ?? "") \(point)"
    
    print(str)
    
}

字符串的长度

// MARK:字符串的长度
func demo1() {
    let str = "hello world你好"
    //返回指定编码的对应的字节数量
    //UTF-8的编码（0~4个），每个汉字是3个字节
    print(str.lengthOfBytes(using: .utf8))
    //字符串长度 -返回字符的个数
    print(str.count)
    //使用NSString中转
    /**
     值 as 类型
     */
    let ocStr = str as NSString
    print(ocStr.length)
}

字符串的遍历

// MARK:字符串的遍历
func demo() {
    let str = "我要飞得更高"
    for c in str {
        print(c)
    }
    
}

字符串的插入和删除

//字符串插入
var welcome = "hello"
     welcome.insert("!", at: welcome.endIndex)//插入一个字符
     print("insertNewCharacters:\(welcome)\n");//打印insertNewCharacters:hello!
      //字符串删除
     welcome.remove(at: welcome.index(before: welcome.endIndex))//删除最后一个字符
     print("removeStrLastCharacters:\(welcome)\n")//打印 removeStrLastCharacters:hello word