C++ Interfaces Tutorial

What is an Interface?

In C++, an interface is a class that only contains pure virtual functions. It cannot be instantiated and must be implemented by other classes. Interfaces are a way to specify the behavior of objects without defining the exact implementation.

#include <iostream>
using namespace std;

class Drawable {
public:
    virtual void draw() = 0;  // Pure virtual function
};

class Circle : public Drawable {
public:
    void draw() override {
        cout << "Drawing Circle" << endl;
    }
};

int main() {
    Drawable* drawable = new Circle();
    drawable->draw();  // Outputs: Drawing Circle
    delete drawable;
    return 0;
}
                

Interface Syntax

In C++, an interface is implemented by declaring a class with pure virtual functions, indicated by `= 0` at the end of the function declaration. The derived class must then implement these functions.

class Printer {
public:
    virtual void print() = 0;  // Pure virtual function
};

class LaserPrinter : public Printer {
public:
    void print() override {
        cout << "Printing using Laser Printer" << endl;
    }
};

int main() {
    Printer* printer = new LaserPrinter();
    printer->print();  // Outputs: Printing using Laser Printer
    delete printer;
    return 0;
}
                

Benefits of Using Interfaces

• Defines a contract that must be followed by any class that implements the interface.
• Enables polymorphism, allowing objects of different classes to be treated as objects of the same type.
• Increases code flexibility by decoupling interface from implementation.