iOS 笔记-incompatible pointer types initializing 'NSMutableString *' with an expression of type 'NSString *'警告处理

NSString *userHeader = [userInfoDictionary objectForKey:@"photo"];
    NSMutableString *mutableuserHeader = [NSMutableString stringWithString:userHeader];
    //设置用户头像
    NSRange range = [mutableuserHeader rangeOfString:@".."];
    [mutableuserHeader replaceCharactersInRange:range withString:@"video"];
    NSMutableString *userHeaderInfo = [Port stringByAppendingString:mutableuserHeader];