NSString *testStr01=@"HelloWord";

        NSString *testStr02=[testStr01 substringToIndex:];//取头（从头到哪），to不包括下标内容

        NSString *testStr03=[testStr01 substringFromIndex:];//去尾（从哪到尾），from包括下标内容

        NSLog(@"testStr02:%@  testStr03:%@",testStr02,testStr03);

        NSRange r={,};//取中间，从哪长度是多少

        NSString*testStr04=[testStr01 substringWithRange:r];

        NSLog(@"testStr04:%@",testStr04);

        //字符串的拼接

        NSString *testStr05 = @"Hello";

        //追加

        NSString *testStr06 = [testStr05 stringByAppendingString:@"World"];

        NSLog(@"testStr06:%@",testStr06);

        //初始化

        NSString *testStr07 = @"Hello";

        NSString *testStr08 = @"World";

        NSString *testStr09 = [NSString stringWithFormat:@"%@%@",testStr07,testStr08];

        NSString *testStr10 = [NSString stringWithFormat:@"Hello%@",testStr08];

        NSLog(@"testStr09:%@",testStr09);

        NSLog(@"testStr10:%@",testStr10);

        //按指定格式(范围)追加内容

        NSString *testStr11 = @"Hello";

        NSString *testStr12 = [testStr11 stringByAppendingFormat:@"%@%@",@"World",@""];

        NSLog(@"testStr12:%@",testStr12);

        //替换

        NSString *testStr13 = @"www.kyle.com.cn";

        NSString *testStr14 = [testStr13 stringByReplacingCharactersInRange:NSMakeRange(, ) withString:@""];

        NSLog(@"testStr14:%@",testStr14);

        //编码集

        //参数 文件的路径 不包括文件名

        NSString *path = @"/Users/apple/Desktop";

        //path = [path stringByAppendingString:@"/test.txt"];

        path = [path stringByAppendingString:@"/test.rtf"];

        //把文件中的内容 读取到字符串中

        //NSString *str20 = [[NSString alloc]initWithContentsOfFile:path];

        NSString *testStr15 = [[NSString alloc]initWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];

        NSLog(@"testStr15:%@",testStr15);

        NSString* use=@"fcp";

        NSString* use1=@"fcp";

        NSString*password=@"";

        NSString*password1=@"";

        if ([use isEqualToString:use1]&&[password isEqualToString:password1]) {

            NSLog(@"登陆成功");

        }

        else{

            NSLog(@"登陆失败");

        }