Xcode 8.0 Swift 3.0 字符串操作

        // 定义一个字符串
        let str = "这是字符串"
        
        // 1.打印字符串长度
        print(str.characters.count)
        
        // 2.打印UTF8编码字节数
        print(str.utf8.count)
        print(str.lengthOfBytes(using: String.Encoding.utf8))
        
        // 3.字符串遍历
        for value in str.characters {
            print(value);
        }
        
        // 4.字符串拼接
        let name = "老王",age = 20
        
        let s1 = "名字是" + name + ",年龄是" + String(age)
        print(s1)
        
        let s2 = "名字是\(name),年龄是\(age)"
        print(s2)
        
        // 5.格式化字符串输入
        let h = 9, m = 50, s = 45
        let time = String(format: "%02d:%02d:%02d", h, m, s)
        print(time)
        
        let time2 = String(format: "%02d:%02d:%02d", arguments: [h, m, s])
        print(time2)
        
        // 6.字符串截取
        // let r1 = "名字是老王,年龄是20"
        
        // startIndex 开始的位置
        // offsetBy 偏移的字符数
        let index = s1.index(s1.startIndex, offsetBy: 2)
        // 从指定位置开始，到字符串结尾
        let r1 = s1.substring(from: index)
        print(r1)

        
        // endIndex 结束位置
        let index2 = s1.index(s2.endIndex, offsetBy: -2)
        // to 从字符开始位置到指定位置结束
        let r2 = s1.substring(to: index2)
        print(r2)
        
        // range 范围
        let range = index..<index2
        let r3 = s1.substring(with: range)
        print("range\(r3)")
        
        // 7.将swift 字符串 转换为 OC 字符串
        let OCString = (s2 as NSString)
        let os = OCString.substring(with: NSMakeRange(2, 4))
        print(os)
        
        let os1 = OCString.substring(from: 2)
        print(os1)
        
        let os2 = OCString.substring(to: 5)
        print(os2)