Classes

A C++ class is a blueprint for creating objects that combines data attributes and functions to define the behavior and state of an entity.

class Person {
  // Class members
};

Class Members

A class is comprised of class members:

• Attributes, also known as member data, consist of information about an instance of the class.
• Methods, also known as member functions, are functions that can be used with an instance of the class.

class City {
  // Attribute
  int population;

  public:
    // Method
    void add_resident() {
      population++;
    }
};

Access Control Operators

C++ classes have access control operators that designate the scope of class members:

• public members are accessible everywhere.
• private members can only be accessed from within the same instance of the class or from friends classes.

class City {
  int population;

  public:
    void add_resident() {
      population++;
    }

  private:
    bool is_capital;
};

Overloading

Redefining operators to work differently with custom data types is called operator overloading in C++. This enables the user to use these operators with objects of their own classes.

The following overloads the + and == operators:

#include <iostream>
using namespace std;

class Point {
public:
  int x;
  int y;

public:
  Point(int x = 0, int y = 0) : x(x), y(y) {}

  Point operator+(const Point& other) const {
    return Point(x + other.x, y + other.y);
  }

  bool operator==(const Point& other) const {
    return (x == other.x) && (y == other.y);
  }

  void display() const {
    std::cout << "Point(" << x << ", " << y << ")\n";
  }
};

int main() {
  Point point1(3, 4);
  Point point2(1, 2);

  Point sum = point1 + point2;
  sum.display();

  Point point3(5, 2);
  Point point4(3, 6);

  bool isEqual = (point3 == point4);
  std::cout << "Points are equal: " << (isEqual ? "true" : "false") << "\n";
}

This will output:

Point(4, 6)
Points are equal: false