{"id":5124,"date":"2025-03-26T09:00:00","date_gmt":"2025-03-26T04:00:00","guid":{"rendered":"https:\/\/afzalbadshah.com\/?p=5124"},"modified":"2024-12-31T08:58:41","modified_gmt":"2024-12-31T03:58:41","slug":"abstract-class-pure-abstract-class-and-interface-in-c-oop","status":"publish","type":"post","link":"https:\/\/afzalbadshah.com\/index.php\/2025\/03\/26\/abstract-class-pure-abstract-class-and-interface-in-c-oop\/","title":{"rendered":"Abstract Class, Pure Abstract Class, and Interface in C++ (OOP)"},"content":{"rendered":"\n

Introduction to Abstract Classes<\/strong><\/h3>\n\n\n\n

An abstract class<\/strong> in C++ is a class designed to be specifically used as a base class. It cannot be instantiated on its own and typically includes at least one pure virtual function<\/strong>.<\/p>\n\n\n\n

A pure virtual function<\/strong> is a function declared within a class that has no implementation relative to the base class and must be implemented by all derived classes.<\/p>\n\n\n\n

Abstract classes are crucial in object-oriented programming to enforce a contract for derived classes.<\/p>\n\n\n\n

Key Definitions<\/strong><\/h3>\n\n\n\n
    \n
  1. Abstract Class<\/strong>: A class with at least one pure virtual function. It serves as a blueprint for derived classes but cannot be instantiated directly.<\/li>\n\n\n\n
  2. Pure Abstract Class<\/strong>: An abstract class where all member functions are pure virtual.<\/li>\n\n\n\n
  3. Interface Class<\/strong>: A class that only contains pure virtual functions and no data members. It defines the “interface” that other classes must implement.<\/li>\n<\/ol>\n\n\n\n

    Code Example: Abstract Class with Pure Virtual Functions<\/strong><\/h3>\n\n\n\n

    Here\u2019s the provided code that demonstrates the concept of abstract classes, including how they are used and enforced through inheritance:<\/p>\n\n\n\n

    Abstract Class and Derived Classes<\/strong><\/h4>\n\n\n\n
    #include <iostream>
    #include <string>
    using namespace std;

    class shape { \/\/ Abstract base class
        public:
        virtual double calculatearea() = 0; \/\/ Pure virtual function
        virtual string getcolor() = 0;      \/\/ Pure virtual function
    };

    class circle : public shape { \/\/ Derived class
        private:
            string color;
            double radius;
        public:
            circle(string c, double r) : color(c), radius(r) {} \/\/ Constructor
            double calculatearea() override {
                return 3.14 * radius * radius; \/\/ Circle area formula
            }
            string getcolor() override {
                return color;
            }
    };

    class rectangle : public shape { \/\/ Derived class
        private:
            string color;
            double length, width;
        public:
            rectangle(string c, double l, double w) : color(c), length(l), width(w) {} \/\/ Constructor
            double calculatearea() override {
                return length * width; \/\/ Rectangle area formula
            }
            string getcolor() override {
                return color;
            }
    };
    <\/code><\/pre>\n\n\n\n
    Explanation of the Classes<\/strong><\/h3>\n\n\n\n
      \n
    1. Abstract Base Class (shape<\/code>)<\/strong>:\n