Why do we need abstract classes in C++?

Question

I\'ve just learned about polymorphism in my OOP Class and I\'m having a hard time understanding how abstract base classes are useful.

What is the purpose of an abstr

Answer 1

Abstract classes allow for compile time protocol enforcement. These protocols define what it means to be a part of a class family.

Another way to think of it is that a abstract class is a contract that your implementing classes must fulfill. If they do not fulfill this contract they cannot be part of the class family and they must be modified to conform to the contract. The provided contract may provide default functionality, but it also leaves it up to the sub-class to define more specific or different functionality while still remaining within the scope of the contract.

For small projects this may not seem useful but for large projects it provides conformity and structure as it provides documentation through the abstract class contract. This makes for more maintainable code and makes for the sub-classes to each have the same protocol making using and developing new sub-classes easier.