CPP Create and Use References

What is a C++ Reference?

• A reference is an alias; when you create a reference, you initialize it with the name of another object, the target.
• So you can create a reference by:
  1. Writing the type of the target object
  2. followed by the reference operator (&),
  3. followed by the name of the reference,
  4. followed by an equal sign,
  5. followed by the name of the target object.
  
  

  int & rNumber = Number;

• DON'T try to reassign a reference or set it to null - it is not permitted in C++.
• DON'T confuse the address-of operator with the reference operator.

    int Number =5;
    int & rNumber = Number; // rNumber is a reference to rNumber 
                            // so to print rNumber or Number result in the same (5)
    //  Using the address-of (&) operator 
    int * pNumber = &Number;    // As rNumber is a reference to 
    int * prNumber = &rNumber;  // Number the addresses have to be equal
    std::cout << "Address:" << pNumber << " = " << prNumber  << "\n";
  

Referencing Objects

• You can make a reference to any created object of any class, but not the class.
• Any public member of a referenced object can be accesses using the dot (.) operator.
  Example using object reference:

  #include <iostream>
  
  class Person
  {
  public:
    Person (int age, int weight){
      this->age = age;
      this->weight = weight;
    }
    ~Person() {}
    int getAge() { return age; }
    int getWeight() { return weight; }
  private:
    int age;
    int weight;
  };
  
  int main()
  {
    Person Ricard(50,80);
    // referencing Ricard
    Person & rRicard = Ricard;
  
    std::cout << "Ricard is: ";
    std::cout << Ricard.getAge() << " years old." << std::endl;
    std::cout << "And Ricard weighs: ";
    // using the reference
    std::cout << rRicard.getWeight() << " kilo." << std::endl;
    return 0;
  }

  When we run this application, the result will be:

  Ricard is: 50 years old.
  And Ricard weighs: 80 kilo.

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