Change base object in derived object

Question

In one of my classes GUI I have a private variable for the class User u. In this GUI class I have a function for the user to login in then check if their account is admin or a normal user and then from that create either a User or Admin object. Admin is derived from user with a few more privileges. How do I set the private variable User u to be either an Admin object or User object after they login.

Read about polymorphism in your favourite C++ book. – molbdnilo Apr 29 '17 at 14:33 — molbdnilo, Apr 29 '17 at 14:33

score -2 · Answer 1 · edited May 23 '17 at 12:02

-2

If the Admin class is extending the User class then you can use User u to represent both of them.

When you need only Admin and you don't know if u is an Admin or User object you can check it like this at runtime:

if(Admin * v = dynamic_cast<Admin*>(u)) {
   // u was safely casted to Admin
   v->doSomething();
}

N.B. dynamic_cast is an operation with big cost you can read here some workarounds.

edited May 23 '17 at 12:02

Community

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answered Apr 29 '17 at 14:38

granmirupa

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I didn't vote, but the proposed solution won't lead to code with good / clean architecture. Sure, an admin "is a" user, but it's probably better to give different users different "roles". – Daniel Jour Apr 29 '17 at 15:23
1

@DanielJour I'm not judging the architecture.. I'm answering to the request of the question. In the question is written *Admin is derived from user* – granmirupa Apr 29 '17 at 15:28

Change base object in derived object

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