Objective-C字符串类NSString与NSMutableString使用

//创建字符串对象
    NSString *str1 = [[NSString alloc] initWithString:@"HelloWorld"];
    NSString *str2 = @"Style";
    str1=@"nice";
    NSLog(@"%@,%@",str1,str2);
    
    //初始化字符串
    NSMutableString *str3 = [[NSMutableString alloc] initWithString:@"Hello"];
    //添加字符串
    [str3 appendString:@"World"];
    NSLog(@"%@",str3);
    //替换字符串
    [str3 setString:@"替换后的字符串"];
    NSLog(@"%@",str3);