Question

Say I have a member function that creates a new object and places it into a data structure (in this case a map) in the class:

Class A
{
    std::map<std::pair<int,int>, BaseClass*> store;
    //...
    public:
    void createObject(?a?)
    {
        BaseClass* temp = new ?a?;
        //place in map...
    };
};

Where ?a? is an argument that can be used to create an object that can be a number of different classes derived from BaseClass. The only way I can think of doing this is by making ?a? an int, and manually typing each type into a switch statement.

Answer 1

Use a member function template. In the context of your example:

template<class T>
void createObject()
{
    BaseClass* temp = new T();
    //place in map...
};

Invoke with:

a.createObject<B>();

Where a is an instance of A, and B is a type derived from BaseClass.