C++ The this Pointer

The this Pointer

In the Constructors chapter, the parameters had short names, like x, y and z. It would be clearer to give them the same names as the attributes, like brand and year.

But then brand = brand; is confusing. Which brand is the attribute, and which is the parameter?

The this pointer solves this. Inside a class, this points to the current object, so this->brand always means the attribute:

class Car {
  public:
    string brand;
    int year;

    Car(string brand, int year) {
      this->brand = brand;
      this->year = year;
    }
};

int main() {
  Car myCar("Ford", 1969);
  cout << myCar.brand << " " << myCar.year;
  return 0;
}

this->brand is the attribute of the object, and brand is the parameter.

The -> Operator

Because this is a pointer, you cannot use a dot to reach the attributes. Instead, you use the arrow operator ->, which is written with a minus sign and a greater than sign.

The arrow is a short way to dereference a pointer and use a dot at the same time. These two lines do the same:

this->brand = brand;
(*this).brand = brand;

Use -> every time you access a member through a pointer. It is shorter, and easier to read.

Use this in Methods

this works in all methods of a class, not only in constructors:

class Player {
  public:
    string name;
    int score = 0;

    void addScore(int score) {
      this->score += score;
    }
};

int main() {
  Player p1;
  p1.name = "Liam";
  p1.addScore(10);
  p1.addScore(5);
  cout << p1.name << " has " << p1.score << " points";
  return 0;
}

When the names are different, you do not need this. But many programmers use it anyway, because it shows clearly that the code changes an attribute of the object.