The mistake has nothing to do with 'int' lacking something. 'int' is totally fine as an user ID or anything else. Everything in computer is essentially an 'int'

The mistake has nothing to do with 'int' lacking something. 'int' is totally fine as an user ID or anything else. Everything in computer is essentially an 'int'. Every character in this text, for example, is an integer. The problem is that 'ban_account' changes data in a user record. Hence it should be a method of a 'User' class. And the 'Message' class should have a way to fetch an instance of 'User' for the sender. Here's the right way: ban_senders_of_messages(messages) { for (i = 0; i < messages.size; ++i) messages[i].sender.ban(); }