this pointer

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Let us understand with an example how and where this pointer is used.

class employee {
     unsigned int m_age;
     unsigned int m_salary;
     employee(unsigned int age, unsigned int salary) {
         m_age = age; // same as this->m_age = age;
         m_salary = salary; //same as this->m_salary = salary

      }

void update(unsigned int age, unsigned int salary) {
         m_age = age; // same as this->m_age = age;
         m_salary = salary; //same as this->m_salary = salary
     }
};
int main() {
     employee emp(40, 45000);
     emp.update(40, 50000);
     return 0;
 }

In the above example, employee object viz. emp is created.
When function viz. update is called using emp object, emp object is implicitly passed in the update function.
emp.update (40, 50000);
converted internally to:
emp.update(&emp, 40, 50000);

Similarly,
void update(unsigned int age, unsigned int salary);
converted internally to:
void update(employee* const this, unsigned int age, unsigned int salary);

  • this pointer is passed as an hidden argument to all the nonstatic member function. This functionality helps in accessing the data member of an object in nonstatic member functions.

  • Friend functions do not have this pointer since they are not members of a class.

  • Static functions do not have this pointer.

  • this pointer is not a member of a class nor it is stored anywhere.

  • this pointer can be used in the constructor as well because when we create an object, memory is allocated by compiler and address of that memory location is passed as a hidden parameter to the constructor which is nothing but a this pointer as shown in the above example


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