C++ Interfaces

What is an Interface in C++?

In C++, an interface is a way to define a contract that a class must adhere to. Although C++ does not have a built-in interface keyword like some other languages, interfaces can be implemented using abstract classes with pure virtual functions.

An interface in C++ is typically an abstract class that has no data members and only pure virtual methods. This ensures that any class inheriting from it will implement all the specified methods, thereby adhering to the defined contract.

Defining an Interface Using Abstract Classes

To define an interface in C++, create an abstract class where all the methods are pure virtual. A pure virtual function is declared by assigning 0 to the method declaration.

Here's a simple example of an interface definition:

Implementing an Interface

Once an interface is defined, any class that inherits from it must implement all its pure virtual functions. This is how C++ enforces the contract defined by the interface.

Below is an example of a class implementing the IShape interface:

Using Interfaces in C++

Interfaces allow for polymorphic behavior in C++. You can use pointers or references to the interface type to work with different objects that implement the interface. This is particularly useful in scenarios where different classes share a common functionality but are implemented differently.

Here's how you can use the IShape interface to handle different shapes:

Benefits of Using Interfaces

Using interfaces in C++ provides several benefits:

• Encapsulation: Interfaces hide the implementation details and expose only the necessary methods.
• Polymorphism: They allow the use of objects of different classes interchangeably.
• Maintainability: They make the code easier to manage and extend, as new classes can be introduced without altering existing code significantly.