1. Objects and Class

2. Object-Oriented Programming (OOP)  Procedure-oriented Programming  Traditional method using command statements  Imperative method  Object-oriented Programming  Views program as interacting objects  Class—template for creating objects  Class encapsulates data and behavior

3. Class Circle  Class Name  Circle  Attributes  radius  Behavior  Calculate area  Calculate volume Circle radius Calculate area Calculate volume

4. Class Circle (cont.) class Circle{ public: Circle(double r){...} // create an object double getRadius(){...} // return radius double area(){...} // return area double volume(){... } // return volume private: double radius; }

5. Using Circle Class #include using namespace std; int main() { Circle cir1(3.0); // create circle obj. Circle cir2(5.0); // another object cout << “Circle of radius “ << 3 << “ has area of << cir1.area() << endl; cout << “Circle of radius “ << 5 << “ has volume of << cir2.volume() << endl; return 0; }

6. Encapsulation of Class  Public section—  Provides an interface to the outside  Shows what methods are available in class  But not how they are implemented  Private section—  Data structure hidden from the outside  Implementation of methods are hidden  “Hidden” means client programs cannot make use of the data structure or method implemenation

7. Separating Interface and Implementation // File: circle.h // Description: function prototypes class Circle{ public: Circle(double r); double getRadius(); double area(); double volume(); private: double radius; }; // Note semicolon

8. Separating Interface and Implementation (cont.) // File: circle.cpp // Description: function implementation Circle:: Circle(double r){... } double Circle::getRadius() {... } double Circle::area(){... } double Circle::volume() {... }

9. Separating Interface and Implementation (cont.) // File: circleTest.cpp // Description: Driver program to test Circle class #include #include “circle.h” using namespace std; int main() { Circle circ(3.0); // create object cout << “Circle of radius “ << 3 << “ has area of << circ.area() << endl; return 0; }

10. Class Triangle  Class Name  Triangle  Attributes  sideA, sideB, sideC  Behavior  Calculate angleA, angleB, angleC  Calculate area  setSideA, setSideB, setSideC Triangle sideA sideB sideC angleA angleB angleC area

11. Class Triangle (cont.) // File: triangle.h // Description: Triangle class interface class Triangle{ public: Triangle(); Triangle(double a, double b, double c); double getSideA(); double getSideB(); double getSideC(); double angleA(); double angleB(); double area(){...}... private: double a, b, c; }

12. Class Triangle (Implement.) // File: triangle.cpp // Description: Methods implementation #include “triangle.h” Triangle::Triangle(){...} Triangle::Triangle(doube a, double b, double c){...} double Triangle::getSideA(){...} double Triangle::getSideB(){...} double Triangle::getSideC(){...} double Triangle::angleA(){...} double Triangle::angleB(){...} double Triangle::area(){...}

13. Class Triangle (Driver) // File: triangleTest.cpp // Description: Driver to test Triangle class #include “triangle.h” #include using namespace std; int main(){ Triangle t(3, 4, 5); cout << “Angle A: “ << t.angleA() << endl; cout << “Angle B: “ << t.angleB() << endl; cout << “Angle C: “ << t.angleC() << endl; cout << “Area: “ << t.area() << endl; return 0; }

14. Method angleA() // Law of Cosines: // a 2 = b 2 + c 2 – 2bc x cos(A) // cos(A) = (b 2 + c 2 – a 2 )/2bc // A = cos -1 (cos(A)) where A is in radians const double PI = 3.14159; const double RAD2DEG = 180/PI; // returns angle A in degrees double angleA(){ double cosA = (b*b + c*c – a*a)/(2 * b * c); return acos(cosA) * RAD2DEG; }

15. Method area() // Heron’s Formula: // area = sqrt(s(s – a)(s – b)(s – c)) // where s = (a + b + c) / 2 #include // returns area of triangle double area(){ double s = (a + b + c) / 2; return sqrt(s * (s-a) * (s-b) * (s-c); }

16. Your Turn  Create a Sphere class (interface and implementations in separate files).  Test the class with a driver.