This Pointer

 

• Every object in C++ has access to its own address through an important pointer called this pointer.
• The this pointer is an implicit parameter to all member functions.
• Therefore, inside a member function, this may be used to refer to the invoking object.
• Friend functions do not have a this pointer, because friends are not members of a class.
• Only member functions have a this pointer.
• The ‘this’ pointer is passed as a hidden argument to all nonstatic member function calls and is available as a local variable within the body of all nonstatic functions.
• ‘this’ pointer is a constant pointer that holds the memory address of the current object.
• ‘this’ pointer is not available in static member functions as static member functions can be called without any object (with class name).
• this pointer is nonmodifiable, assignments to this are not allowed.

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Class demo

{

public :

int mn;

void fun( int mn )
{
   month = mn;              // These three statements
   this -> month = mn;       // are equivalent
   (*this).month = mn;
}

};

when we call this function like

demo obj;

obj.fun(20);

then it is converted as

fun(&obj, 20);

syntax of the function fun is

void fun(demo * const this, int mn);

In this case first parameter is considered as a this pointer.

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Following are the situations where ‘this’ pointer is used:

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

class demo

{

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; }

};

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• To return reference to the calling object

class demo

{

public:

int a;

demo()

{

a = 10;

printf("demo constructor");

}

demo& fun ()

{

//

// Some processing on caller object and return modified object

//

this->a = 20;

return *this;

}

};

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