What are the best practices for using abstract classes in C++?

What are the best practices for using abstract classes in C++?

When using abstract classes in C++, it's important to ensure that they provide a clear interface for derived classes. Here are some best practices:

1. Use pure virtual functions to define the interface.
2. Keep the abstract class focused on a single responsibility.
3. Avoid implementing any functionality in the abstract class unless necessary.
4. Use protected constructors to prevent instantiation of the abstract class.

Can you explain what a pure virtual function is?

A pure virtual function is a function declared in a base class that has no implementation and is meant to be overridden in derived classes. It is defined by assigning 0 in its declaration, like this: virtual void myFunction() = 0;. This makes the class abstract.

What are some common mistakes to avoid with abstract classes?

Common mistakes include:

1. Implementing too much functionality in the abstract class.
2. Not providing a clear interface for derived classes.
3. Forgetting to declare the destructor as virtual, which can lead to resource leaks.

How do I decide when to use an abstract class instead of an interface?

Use an abstract class when you want to provide some shared functionality or state among derived classes. Use an interface when you want to define a contract without any implementation. If you need to share code, go for an abstract class; if not, an interface is preferable.