C++ this pointer

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C++ this pointer

C++ language uses a unique keyword called “this” to represent an object that invokes a member function. this is a pointer to the object for which “this” function was called. for example The function calling A.max() set the pointer this to the address of the object A.
The starting address is the same as the address of the first variable A in the class structure

This unique pointer is automatically passed to a member function whenever it is called . The pointer this acts as an implicit argument to all the member functions. take e example

class ABC
{
int a;
…..
…..
};

in the above example private variable a can be used directly inside a member function like

item *it_ptr;

a=145;
we can also use the following statement in below to do same activity this->a=123;

since c++ programming permits the use of shorthand form a=145 we have not been using the pointer this explicitly so far. when we have been implicitly using the pointer this when overloading the operators using the member function re-call that when a binary operator overloaded by using a member function. we pass only one argument to the function. The other argument is implicitly pass using the pointer “this” . one of the important application of the pointer this is to return the object it points to. in the below take a example to understand

person & person :: greater(person & X)
{
if(x.age>age)
return x; // argument object
else
return *this; // invoking the object
}
suppose we invoke this function by the calling
max=A.greater(B);

The function will return the object B(argument object) if the age of the person B is greater than of A, otherwise this will return the object A (invoking object) using the pointer this, remember The dereference operator * produces the contents at the address contained in the pointer.

A complete program to use of the this is given in below

this Pointer
#include <iostream>
#include <cstring>
using namespace std;
class person
{
char name[20];
float age;
public:
person(char *s, float a)
{
strcpy(name,s);
age=a;
}
person & person :: greater(person &x)
{
if(x.age>=age)
return x;
else
return *this;
}

void display()
{
cout << "Name:" << name << "\n"
<< "age:" << age << "\n";
}
};
int main()
{
person p1("john",37.50),
p2("ahmed",29.0),
p3("Hebber",40.25);
person p=p1.greater(p3); //p3.greater(p1)
cout << "Elder person is: \n";
p.display();
p=p1.greater(p2); // p2.greater(p1)
cout << "Elder person is: \n";
p.display();
return 0;
}

Elder person is:
Name: Hebber
Age: 40.25
Elder person is:
NAme: John
Age: 37.5

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