Question

Is it possible to specifiy a template as a member but not know all the details? Or rather how can I work around this.

Example doesn’t work but might show you what I’m trying to achieve.

template<typename T>
struct Foo {
   ///blah...
};

struct Bar {
    Foo* m_foo;
};

Bar in this case is a base class, and depending on the derived classes I wont know the full details of Foo

Answer 1

You can either make Bar a template class as well so it can pass that template argument along to Foo, or else you can make all the Foo<T> variations inherit from a common interface (in C++, an interface is just an abstract class with no implementation, all members are pure virtual functions) and then Bar can point to that interface.

The first way is better if Bar is just going to provide some functionality which will be reused by a bunch of derived classes.

The second way is better if descendants of Bar are going to be used polymorphically.