//MARK: - 遍历字符串
    func demo5(){
        let str : String = "飞哪里去了"
        
        //遍历
        for c in str.characters {
            print(c)//带有换行效果,类似nslog
        }
    }
    
    //MARK: - 拼接字符串
    func demo4(){
        let name = "zhangsan"
        let age = 8
        let point = view.center
        
        //格式"\(变量/常量)"
        print("\(name)年龄\(age)\(point)")
    }
    
//MARK: - 字符长度
    func demo3(){
        let name = "hello world 你好世界"
        
        //一个中文对应的 UTF8编码 占 3 个字节,UTF8占 1-4个字符
      print(name.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
        
        //获得字符串中的字符的个数
        print(name.characters.count)

        //as 是类型转换 = > 
        let ocName = name as NSString
        print(ocName.length)
    }

 //MARK: - 格式化字符串
    func demo2(){
        let h = 7
        let m = 0
        let s = 8
        
        let dateString = "\(h):\(m):\(s)"
        print(dateString)
        
      
        //数组生成格式化字符串
        let dateString1 = String(format: "%02d:%02d:%02d", arguments:[h,m,s])
        print(dateString1)
        
        let dateString2 = String(format: "%02d:%02d:%02d",h,m,s)
        print(dateString2)
    }
    
//MARK: - 截取字符串
    func demo(){
        let str = "我们一起去飞"
        
        //方法一使用NSString 
        let subStr = (str as NSString).substringWithRange(NSMakeRange(2, 4))
        print(subStr)
        
        //方法二 从字符起始位置开始,将索引递进的,下标位置到末尾
        let subStr2 = str.substringFromIndex(str.startIndex.advancedBy(4))
        print(subStr2)//去飞
        
        //从开始的位置到下标位置,注意不能为负数,会越界
        let subStr3 = str.substringToIndex(str.startIndex.advancedBy(3))
        print(subStr3)//我们一
        
        //xcode 7 beta 5开始固定格式
        let starIndex = str.startIndex
        let endIndex = str.endIndex
        
        //若是范围越界会崩溃
        let subStr4 = str.substringWithRange(str.startIndex..<str.endIndex)
        print(subStr4)
    }