Inheritance

OOP Inheritance (Backbone of the OOP) Instructor Mr.Fasee Ullah CUSIT Peshawar

C++ and inheritance The language mechanism by which one class acquires the properties (data and operations) of another class Base Class (or superclass ): It’s the main class, where data members and function members can inherit Derived Class (or subclass ): the class that inherits data members and function members from base class

What a derived class doesn't inherit The base class's constructors and destructor

What a derived class can add New data members New member functions (also overwrite existing ones) New constructors and destructor

When a derived-class object is created & destroyed Space is allocated (on the stack or the heap) for the full object (that is, enough space to store the data members inherited from the base class plus the data members defined in the derived class itself) The base class's constructor is called to initialize the data members inherited from the base class The derived class's constructor is then called to initialize the data members added in the derived class The derived-class object is then usable When the object is destroyed (goes out of scope or is deleted) the derived class's destructor is called on the object first Then the base class's destructor is called on the object Finally the allocated space for the full object is reclaimed

Advantages of inheritance When a class inherits from another class, there are three benefits: (1) You can reuse the methods and data of the existing class (2) You can extend the existing class by adding new data and new methods (3) You can modify the existing class by overloading its methods with your own implementations

Access Rights of Derived Classes Type of Inheritance

Inheritance For instance, graphics objects might be defined as follows: This hierarchy could, of course, be continued for more levels. Each level inherits the attributes of the above level. Shape is the base class. 2-D and 3-D are derived from Shape and Circle, Square, and Triangle are derived from 2-D. Similarly, Sphere, Cube, and Tetrahedron are derived from 3-D.

Inheritance Concept Rectangle Triangle Polygon Point Circle 3D-Point

Parent and Child Classes Inheritance Concept Rectangle Triangle Polygon class Polygon { private: int width, length; public: void set(int w, int l); } class Rectangle{ private: int width, length; public: void set(int w, int l); int area(); } class Triangle{ private: int width, length; public: void set(int w, int l); int area(); }

Inheritance Concept Rectangle Triangle Polygon class Polygon { protected: int width, length; public: void set(int w, int l); } class Rectangle : public Polygon { public: int area(); } class Rectangle{ protected: int width, length; public: void set(int w, int l); int area(); }

Inheritance Concept Rectangle Triangle Polygon class Polygon { protected: int width, length; public: void set(int w, int l); } class Triangle : public Polygon { public: int area(); } class Triangle : public polygon{ protected: int width, length; public: void set(int w, int l); int area(); }

Inheritance Concept Point Circle 3D-Point class Point { protected: int x, y; public: void set(int a, int b); } class Circle : public Point { private: double r; } class 3D-Point: public Point { private: int z; } x y x y r x y z

Example1 on Inheritance #include<iostream.h> #include<conio.h> Class test { Private: int x; Public: int y; Protected: int z; }; Class test1: public test{ Public: int a; a=y; }; Main(){ Test t1; t1.y; t1. z; //error }

Example2 on Inheritance class X { public: void message(){ Cout<<“Welcome to Inheritance”; } }; class Y: public X { }; Void main() { X x; Y y; x.message(); y.message(); //for verification, call Y }

Example3 on Inheritance //inheritance program... #include<iostream.h> #include<conio.h> class point { int x,y; public: void getxy(int a,int b) { x=a; y=b; } }; class circle: public point{ int radius; public: void getradius(int r) { radius=r; } void area(){ int area; area=3.142*radius*radius; cout<<"Area of circle is "<<area; } }; void main(){ circle c; c.getxy(3,5); c.getradius(5); c.area(); getch(); }

Assignment #2 What are the practical issues in Inheritance.? Submission: Next Week

Inheritance

More Related Content

What's hot (20)

Similar to Inheritance (20)

Inheritance