Establish connection between parent and child class

Question

Assume you have two classes, a Manager who holds a set of Clients and the Client holds a backreference to the Manager.

class Manager {
public:
    void addClient(Client* client) {
        m_clients.push_back(client);
        client->setManager(this);
    }
private:
    std::list<Client*> m_clients;
};

class Client {
public:
    void setManager(Manager* manager) {
        m_manager = manager;
    }

private:
    Manager* m_manager;
};

The confusing, probably even dangerous feature of this API is that Client exposes a setManager() method that can be called by anyone, yet should only be called by the Manager::addClient() method.

assert(manager->hasClient(this)) in setManager() would prevent wrong calling at runtime, however I would prefer a solution that doesn't allow the user to call methods he isn't supposed to call.

What would be common solution? I don't

want to use friend to expose all of Clients members to Manager so that he can establish the binary connection in addChild()
want both classes to share some kind of Composite base class. They should remain unrelated inheritancewise.

You should change the question to A solution that doesn't allow the user to call methods he isn't supposed to call. Have a look at Facade, Interface, Proxy, Adaptor, Bridge. I would also say you can name the method do_never_call_me_unless_you_know_what_for_add_client — User, May 14 '14 at 15:08
Could you simply check in setManager() whether m_manager has already been set? — Greg Hewgill, May 14 '14 at 20:09

score 1 · Answer 1 · edited May 23 '17 at 12:40

One fairly standard approach would be to make Client::setManager protected and declare Manager::addClient as a friend function in Client. This will allow Manager::addClient access to all of Client's private and protected members, not just Client::setManager, but is more encapsulated overall than a public Client::setManager.

Establish connection between parent and child class

1 Answers1