How Do I Define and Implement Interfaces in C Using Abstract Base Classes?

Declaring Interfaces in C

Question:

How can I define a class representing an interface in C ? Is this achieved through an abstract base class?

Answer:

Yes, an interface in C can be defined as an abstract base class. To create an interface:

1. Declare a pure abstract class: This class should contain only pure virtual methods, which have no implementation. The methods serve as placeholders and force derived classes to implement them.

class IDemo {
public:
    virtual void OverrideMe() = 0;
};

2. Derived classes: Classes that inherit from the interface must implement all pure virtual methods. They provide the concrete implementation of the interface.

class Child : public IDemo {
public:
    virtual void OverrideMe() {
        // Implement the method here
    }
};

3. Virtual destructor (optional): Consider adding a virtual destructor to the interface. This allows safe pointer ownership transfer without exposing the concrete derived class.

class IDemo {
public:
    virtual ~IDemo() {}
    virtual void OverrideMe() = 0;
};

Additional Notes:

• Unlike in other languages, C interfaces do not support multiple inheritance.
• The destructor does not require a body since the interface has no concrete members.
• Some compilers may have issues with empty virtual destructors, so it's recommended not to include a body.
• Using virtual and inline functions together for the destructor is acceptable.

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