Класс и объект в C++

// Cout command used to print a string to the screen:

cout << "One";


// Print a string "One " and next is string "Two ".

cout << "One "  << "Two ";


// Print a string "One " next string "Two " and next number 3.

cout << "One " << "Two "  <<  3 ;

// Print a string "One" and next is newline character.

cout << "One" << endl;

#include <iostream>
using namespace std;

namespace mynamespace {

  class Rectangle {

      private:
          int width;
          int height;

      public:
          Rectangle();
          Rectangle(int, int);

      public:
          int getArea() {
              return  width * height ;
          }
          int getWidth() {
              return width;
          }
          int getHeight()  {
              return height;
          }
  };

  Rectangle::Rectangle() {
      width = 10;
      height = 5;
  }

  Rectangle::Rectangle(int a, int b) {
      width = a;
      height = b;
  }
}


// Declare use libraries located in the namespace 'mynamespace'.
// (Including Rectangle (Because it is in this namespace) ).
using namespace mynamespace;

int main() {

// Create a Rectangle 'rect1' from Constructor Rectangle(int, int).
// Value 5 is assigned to the width, the value 4 is assigned to the height.
Rectangle rect1(5, 4);

// Create a Rectangle 'rect2' from default Contructor Rectangle().
// width, height are assigned default values
Rectangle rect2;

cout << "rect1:" << endl;
// Call method to get with
cout << " width: " << rect1.getWidth() << endl;
// Call method to get heght
cout << " height: " << rect1.getHeight() << endl;

// Call the method to calculate the area.
cout << " area: " << rect1.getArea() << endl;

cout << "rect2:" << endl;
cout << " width: " << rect2.getWidth() << endl;
cout << " height: " << rect2.getHeight() << endl;
cout << " area: " << rect2.getArea() << endl;
return 0;
}

#include <iostream>
#include <math.h>
using namespace std;


namespace mynamespace {

    class Circle {

        private:
            int radius;

        public:
            Circle() {
                radius = 100;
            }
            // Constructor with one parameter.
            // Assign value for radius field.
            Circle(int r) {
                radius = r;
            }

        public:
            float getArea() {
                // M_PI is a constant defined in <math.h>
                return  M_PI * radius* radius ;
            }
            // Method returns radius
            // (The content of this method is written in another place)
            int getRadius();

            // Method to assign a new value for the radius
            void setRadius(int r){
                radius = r;
            }
    };

    // Content of getRadius()
    int Circle::getRadius() {
         return radius;
    }
}

// Declare to use the namespace 'mynamespace'.
using namespace mynamespace;

int main() {

    // Create a Circle with radius = 5.
    Circle circle1(5);

    // Create a Circle with defalt radius (100).
    Circle circle2;

    cout << "Circle 1:" << endl;
    cout << " radius: " << circle1.getRadius()  << endl;
    cout << " area: " << circle1.getArea() << endl;

    cout << "Circle 2:" << endl;
    cout << " radius: " << circle2.getRadius() << endl;
    cout << " area: " << circle2.getArea() << endl;

    // Set new value for the radius.
    circle2.setRadius(200);

    cout << "Circle 2 (After set new Radius):" << endl;
    cout << " radius: " << circle2.getRadius() << endl;
    cout << " area: " << circle2.getArea() << endl;

    return 0;

}

#ifndef PERSON_H_
#define PERSON_H_

// Using string
#include <string>

// Using namespace std (to use string, cout,..)
using namespace std;

namespace mynamespace {

  
    class Person {

        private:
            // A field
            string name;

        public:
            // Default constructor
            Person();
            // Constructor with one parameter.
            Person(string);

            // Destructor.
            virtual ~Person();



        public:
            // Method return name of person.
            string getName();
            // Set new name for person.
            void setName(string);

    };

}

#endif

// Inclure Person.h
#include "Person.h"
#include <iostream>
#include <string>

using namespace std;

namespace mynamespace {

    Person::Person() {
        // Default name.
        name = "Anonymous";
    }

    Person::Person(string name) {
        // Assign value to field of Person.
        // Using this -> name to refers to name field of Person.
        // (To avoid confusion with the parameter 'name').
        this-> name = name;
    }

    // Destructor, same name with name of class and has no parameters.
    Person::~Person() {
        cout<< "Destructor called" <<endl ;
    }


    // Content of method getName().
    string Person::getName()  {
        return this-> name;
    }

    // Set new name for person.
    void Person::setName(string newName)  {
        // Assign new name.
        name = newName;
    }

}

#include "Person.h"
#include <iostream>
#include <string>

using namespace std;

 
using namespace mynamespace ;

int main() {

    // Create a Person object.
    Person billGate("Bill Gate");

    cout << "billGate.getName(): " << billGate.getName() << endl;

    // Create a Person from default contructor.

    Person aPerson ;

    cout << "aPerson.getName(): "<< aPerson.getName() << endl;

    cout << "aPerson set new name" << endl;

    // Set new name for aPerson.
    aPerson.setName("Markus Hess");

    cout << "aPerson.getName(): " << aPerson.getName() << endl;

    return 0;


}