CPP References and const Modifier/h1>

Using const specifier with the Method's arguments.

• If we in the Constructor do not want to give any possibility to change the integers original values then the Constructor must be as:

  // This Constructor take two arguments of 
  // reference to const integer
    Person (const int & rAge, const int & rWeight){
  // Set the age and weight 
  // We cannot changed the original integers now, only get them;
      this->age = rAge;       
      this->weight = rWeight; 
    }

• If the argument to a method is of const object reference and you want to access any method in that object, these methods must be const specified :
  Example of a const object reference using methods of the object:

  #include <iostream>
  
  class Person {
  public:
  // This Constructor take two arguments of 
  //  reference to integer
    Person (int & age, int & weight){
  // Set the age and weight 
      this->age = age;
      this->weight = weight;
    }
  // This Constructor take arguments of 
  // reference to const object of Person
    Person (const Person & pPerson){
      this->age = pPerson.getAge()+1;
      this->weight = pPerson.getWeight()+10;
    }
     ~Person() {}
  // As we are using these methods in the last 
  // Constructor they must be supplied with the const specifier
    int getAge() const { return age; }
    int getWeight() const { return weight; }
  
  private:
    int age;
    int weight;
  };
  
  int main() {
    int age = 40;
    int weight = 60;
  // Using Constructor that take two arguments of 
  // reference to integer
    Person * pRicard = new Person(age, weight);
    std::cout << "Ricard is: ";
    std::cout << pRicard->getAge() << " years old.\n" ;
    std::cout << "And Ricard weighs: ";
    std::cout << pRicard->getWeight() << " kilo.\n\n" ;
  // Using Constructor that take arguments of 
  // reference to const object of Person
    Person * pObama = new Person(*pRicard);
    std::cout << "Obama is: ";
    std::cout << pObama->getAge() << " years old.\n" ;
    std::cout << "And Obama weighs: ";
    std::cout << pObama->getWeight() << " kilo.\n\n" ;
  
    return 0;
  }

  When we run this application the result will be:

  Ricard is: 40 years old.
  And Ricard weighs: 60 kilo.
  
  Obama is: 41 years old.
  And Obama weighs: 70 kilo.

  You can download this example here (needed tools can be found in the right menu on this page).