Inheritance Math 130 B Smith: Consider using the example in SAMS Teach Yourself C++ in 24 hours B Smith: Consider using the example in SAMS Teach Yourself C++ in 24 hours

2 Overview to cover  sub title also cover this is a box a callout this is code this is also code

3 Motivation Want to reuse code Don’t want to destroy the perfection of the existing code that we’ll reuse Goal: Use C++ classes without breaking the existing code Solution: Create a new class as a type of an existing class  inherit the features you’re interested in

4 Example 1 class Circle { protected: double radius; public: Circle(double = 1.0); // constructor double getArea(); };

5 // class implementation Circle::Circle(double r) // constructor { radius = r; } double Circle::getArea() // this calculates an area { return(PI * radius * radius); } Implementation

6 class Cylinder : public Circle // Cylinder is derived from Circle { protected: double length; // add one additional data member and public: // two additional function members Cylinder(double r = 1.0, double l = 1.0) : Circle(r), length(l) {} double getArea(); }; // class implementation double Cylinder::getArea() // this calculates a volume { return (length * Circle::getArea()); // note the base function call } class Circle { protected: double radius; public: Circle(double = 1.0); double getArea(); }; B Smith: Insert pictures here to show how one builds/inherits attributes from the other B Smith: Insert pictures here to show how one builds/inherits attributes from the other

7 Example 2 class one // the base class { protected: float a; public: one(float = 2); // constructor float f1(float); // a member function float f2(float); // another member function };

8 Implementation // class implementation one::one(float val) // constructor { a = val; } float one::f1(float num) // a member function { return(num/2); } float one::f2(float num) // another member function { return( pow(f1(num),2) ); // square the result of f1() }

9 class two : public one // the derived class { public: float f1(float); // this overrides class one's f1() }; // class implementation float two::f1(float num) { return(num/3); }

10 Driver Code int main() { one object_1; // object_1 is an object of the base class two object_2; // object_2 is an object of the derived class // call f2() using a base class object call cout << "The computed value using a base class object call is " << object_1.f2(12) << endl; // call f2() using a derived class object call cout << "The computed value using a derived class object call is " << object_2.f2(12) << endl; return 0; }

11 Example 3 class One // the base class { protected: float a; public: One(float = 2); // constructor virtual float f1(float); // a member function float f2(float); // another member function };

12 Implementation // class implementation One::One(float val) // constructor { a = val; } float One::f1(float num) // a member function { return(num/2); } float One::f2(float num) // another member function { return( pow(f1(num),2) ); // square the result of f1() }

13 class Two : public One // the derived class { public: virtual float f1(float); // this overrides class One's f1() }; // class implementation float Two::f1(float num) { return(num/3); }

14 int main() { One object_1; // object_1 is an object of the base class Two object_2; // object_2 is an object of the derived class // call f2() using a base class object call cout << "The computed value using a base class object call is " << object_1.f2(12) << endl; // call f2() using a derived class object call cout << "The computed value using a derived class object call is " << object_2.f2(12) << endl; return 0; }

15 Summary this is code