In C++, interfaces are implemented using pure virtual functions, providing a powerful mechanism for defining abstract contracts that derived classes must fulfill. This concept is fundamental to achieving polymorphism and creating flexible, extensible code structures.
Pure virtual functions are special virtual functions that have no implementation in the base class. They are declared by assigning 0 to the function declaration:
virtual returnType functionName(parameters) = 0;
A class containing at least one pure virtual function is called an abstract class. Such classes cannot be instantiated directly but serve as interfaces for derived classes.
To create an interface in C++, define a class with only pure virtual functions:
class Shape {
public:
virtual double area() = 0;
virtual double perimeter() = 0;
virtual ~Shape() {} // Virtual destructor
};
This Shape class acts as an interface, defining a contract for any class that inherits from it. Derived classes must implement all pure virtual functions to be instantiable.
To implement an interface, create a derived class and provide implementations for all pure virtual functions:
class Circle : public Shape {
private:
double radius;
public:
Circle(double r) : radius(r) {}
double area() override {
return 3.14159 * radius * radius;
}
double perimeter() override {
return 2 * 3.14159 * radius;
}
};
override
keyword when implementing interface functions in derived classes for better code clarity and compiler checks.Interfaces, implemented through pure virtual functions in C++, provide a powerful tool for designing flexible and extensible software systems. By mastering this concept, you can create more modular, maintainable, and scalable code structures in your C++ projects.
Remember to explore related topics such as inheritance and virtual functions to gain a comprehensive understanding of object-oriented programming in C++.