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Interface

In C++, there is no direct keyword or construct for defining an interface like there is in some other programming languages (e.g., Java or C#). However, it can achieve the concept of an interface using abstract classes and pure virtual functions. An interface, in the context of C++, it can be thought of as a class that only contains declarations of member functions (pure virtual functions) without any actual implementations. Derived classes then provide concrete implementations for these functions.

Here's how it can create an interface-like structure in C++:

1. Abstract Class:

Create an abstract class, which is a class that contains one or more pure virtual functions. A pure virtual function is declared with the virtual keyword followed by = 0, and it has no implementation in the base class.

Program:

class Interface {
public:
    virtual void someFunction() = 0; // Pure virtual function
    virtual int anotherFunction() const = 0; // Another pure virtual function
};
2. Derived Classes:

Create derived classes that inherit from the abstract class and provide concrete implementations for the pure virtual functions. These derived classes must implement all the pure virtual functions to be considered concrete classes.

Program:

class ConcreteClass : public Interface {
public:
    void someFunction() override {
        // Implementation for someFunction
    }

    int anotherFunction() const override {
        // Implementation for anotherFunction
    }
};
3. Using the Interface:

it can use the interface by creating objects of the concrete classes or using pointers or references to the base class (the interface itself). This allows to work with objects in a polymorphic manner.

Program:

int main() {
    ConcreteClass obj;

    Interface* ptr = &obj; // Using a pointer to the base class
    ptr->someFunction();   // Calls ConcreteClass::someFunction()

    return 0;
}

It's important to note that in C++, it can inherit from multiple abstract classes (multiple inheritance) to implement multiple interfaces if needed.

While C++ doesn't have a specific keyword for interfaces, this approach using abstract classes and pure virtual functions achieves similar functionality. I0t allows to define a common interface for classes that need to adhere to a specific contract while still allowing each class to provide its own implementation.


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