Finding most efficient method for large switch-case and if-else

Question

I'm learning OOP and I found that you can use polymophism to replace switch-case and if-else. But I still wonder how to do that most efficiently. Here is my manage class for managing info of 5 different class:

class Manage
{
private:
    Human *List[100];
    int iObject_num;
public:
    Manage(){
        iObject_num=0;
    }
    ~Manage(){
        delete List;
    }
    void vInList()
    {
        int choice;
            do
                {
                    Menu(); //the menu has 6 choices
                    fflush(stdin);
                    cin>>choice;
                    switch(choice)
                    {
                    case 1:{
                        List[iObject_num]= new Student;
                        List[iObject_num]->vInPrivate(); // input the protected info of base class
                        List[iObject_num]->vIn();// input the private of each child class
                        iObject_num++;
                        break;}
                    case 2:{
                        List[iObject_num]= new Undergrad;
                        List[iObject_num]->vInPrivate();
                        List[iObject_num]->vIn();
                        iObject_num++;
                        break;}
                    case 3:{
                        List[iObject_num]= new Worker;
                        List[iObject_num]->vInPrivate();
                        List[iObject_num]->vIn();
                        iObject_num++;
                        break;}
                    case 4:{
                        List[iObject_num]= new Actor;
                        List[iObject_num]->vInPrivate();
                        List[iObject_num]->vIn();
                        iObject_num++;
                        break;}
                    case 5:{
                        List[iObject_num]= new Musician;
                        List[iObject_num]->vInPrivate();
                        List[iObject_num]->vIn();
                        iObject_num++;
                        break;}
                    case 0:
                        cout<<"Exiting...\n";
                        break;
                    default:
                        cout<<"Invalid!\n";
                    }
                } while(choice!=0);

    };
    void vOutList(){
        cout<<"Total number of input: "<<iObject_num<<"\n";
        for (int i=0;i<iObject_num;i++)
        {
            List[i]->vOutPrivate();
            List[i]->vOut();
            cout<<"\n";
        }
    }
};

I've been searching for answer but most of them all told the same thing: override the virtual function. I've already do that as you can see, but if there's more than 5 classes, I will have to do switch-case more than 5 times to call each class' function?

Answer 1

You can create factory for example HumanFactory

class HumanFactory
{
public:
    virtual Human* createHuman() = 0;
    virtual ~HumanFactory() {}
};

class StudentFactory : public HumanFactory
{
public:
    Human* createHuman() override { return new Student; }
};

and all the concrete humans can be added to list in

class Manage
{
private:
    std::vector<Human*> humans;
    std::vector<HumanFactory*> factories;
    
// register factory 
void registerFactory(HumanFactory* factory)
    {
        factories.push_back(factory);
    }

void vInList()
    {
        int choice;
        do
        {
            Menu(); // The menu has 6 choices
            std::cin >> choice;

            if (choice >= 1 && choice <= factories.size())
            {
                Human* human = factories[choice - 1]->createHuman();
                human->vInPrivate();
                human->vIn();
                humans.push_back(human);
            }
            else if (choice != 0)
            {
                std::cout << "Invalid choice!\n";
            }
        } while (choice != 0);
    }

int main()
{
    Manage manager;
    manager.registerFactory(new StudentFactory());
    // Register other factories as needed

    manager.vInList();
    manager.vOutList();

    return 0;
}

I have provided code, not fully finished but I think will give you idea how to replace switch.