C++ Vector iterate over abstract class

Question

Background info: Me and a couple of friends are building this platform game in C++ with the help och sfml and box2d for a school assignment. One of the requirements is that we follow the "MVC pattern". We have created classes like Bullet and Character for the model. And BulletView and CharacterView (both inherits sf::Drawable which is an abstract class) for the view. Instead of duplicating code for drawing and have two methods drawBullets and drawCharacter like this ``` void WorldView::drawBullets() { std::vector::iterator it; for ( it = bullets.begin() ; it < bullets.end(); it++ ) window->draw(**it); } void WorldView::drawCharacters() { std::vector::iterator it; for ( it = characters.begin() ; it < characters.end(); it++ ) window->draw(*it); } ``` I would like a more generic method using polymorhism which would look something like this: ``` void WorldView::drawVector(const std::vector& vector) { std::vector::iterator it; for…

Accepted Answer

The problem is that the polimorphism doesn't work at the level of the vectors, but at the levevel of the pointers they contain. So `std::vector` can never be passed as an `std::vector`, since they are completely different types. However, you can fill an `std::vector` with pointers to `Derived*`. So, you should declare your bullet vector as ``` std::vector bullets; ``` and fill it with `BulletView*`, for example: ``` bullets.push_back( new BulletView( some args) ); drawVector(bullets); ``` Note: In the code above I am sidestepping the issue of dynamically allocated object ownership. Obviously some mechanism must be in place for deleting the `BulletViews` at the right moment.

C++ Vector iterate over abstract class

Solution

Problem