Home | Projects | Notes > C++ Programming > this Pointer

this Pointer

Introduction

• this is a reserved keyword that contains the address of the current object.

  • It's a pointer to the object that's currently being used by the class member methods.

• Can only be used within the class scope

• All member access is done via the this pointer.

  • C++ allows you to use member names directly. And, behind the scenes, it's actually using this pointer.

• Can be used by the programmer

  • To explicitly access data member and methods

  • To determine if two objects are the same

  • Can be dereferenced (*this) to yield the current object

  • When overloading the assignment operator

Examples

• Account class

  xxxxxxxxxx
  4
  1
  void Account::set_balance(double bal)
  2
  {
  3
      balance = bal;  // 'this->balance' is implied
  4
  }
  

  this pointer can be used to disambiguate identifier

  xxxxxxxxxx
  5
  1
  void Account::set_balance(double balance)
  2
  {
  3
      // balance = balance        // Ambiguous (which balance?)
  4
      this->balance = balance;    // Unambiguous
  5
  }
  

• To determine object identity

  Sometimes it is useful to know if two objects are the same object

  xxxxxxxxxx
  8
  1
  int Account::compare_balance(const Account &other)
  2
  {
  3
      if (this == &other)
  4
          std::cout << "The same objects" << std::endl;
  5
      ...
  6
  }
  7
  
  8
  jack_account.compare_balance(jack_account);
  

  L3: When the compare logic is involved or computationally expensive, then a quick check to see if the objects are the same could help performance.