When to use this

https://www.geeksforgeeks.org/this-pointer-in-c/

When local variable’s name is same as member’s name

#include<iostream> 
using namespace std; 
  
/* local variable is same as a member's name */
class Test 
{ 
private: 
   int x; 
public: 
   void setX (int x) 
   { 
       // The 'this' pointer is used to retrieve the object's x 
       // hidden by the local variable 'x' 
       this->x = x; 
   } 
   void print() { cout << "x = " << x << endl; } 
}; 
  
int main() 
{ 
   Test obj; 
   int x = 20; 
   obj.setX(x); 
   obj.print(); 
   return 0; 
} 

Output:

x = 20

To return reference to the calling object

#include<iostream> 
using namespace std; 
  
class Test 
{ 
private: 
  int x; 
  int y; 
public: 
  Test(int x = 0, int y = 0) { this->x = x; this->y = y; } 
  Test &setX(int a) { x = a; return *this; } 
  Test &setY(int b) { y = b; return *this; } 
  void print() { cout << "x = " << x << " y = " << y << endl; } 
}; 
  
int main() 
{ 
  Test obj1(5, 5); 
  
  // Chained function calls.  All calls modify the same object 
  // as the same object is returned by reference 
  obj1.setX(10).setY(20); 
  
  obj1.print(); 
  return 0; 
} 

Output:

x = 10 y = 20