this Pointer in C++

In this lesson: Use the this pointer in C++ to refer to the current object and chain methods — examples with output. In Hindi & English.

What is the this pointer?

Inside every non-static member function there is a hidden pointer called this, which points to the object the function was called on. When you write obj.method(), inside method the pointer this holds the address of obj.

Disambiguating names

The most common use: when a parameter has the same name as a data member, this-> makes clear which one you mean:

#include <iostream>
using namespace std;
class Box {
    int width;
public:
    void setWidth(int width) {
        this->width = width;    // member = parameter
    }
    int getWidth() { return width; }
};
int main() {
    Box b;
    b.setWidth(50);
    cout << b.getWidth();   // 50
}

Here this->width is the member; plain width is the parameter.

Returning *this for chaining

If a member function returns *this (the current object by reference), you can chain calls one after another:

class Builder {
    int x = 0, y = 0;
public:
    Builder& setX(int v) { x = v; return *this; }
    Builder& setY(int v) { y = v; return *this; }
    void show() { cout << x << "," << y << "\n"; }
};
int main() {
    Builder b;
    b.setX(3).setY(7).show();   // chained calls
}

Each setter returns the same object, so the next call continues on it.

Comparing objects

this also lets a function compare the current object with another, for example to check for self-assignment: if (this == &other) return *this;.

this and static functions

A static member function has no this pointer, because it is not tied to any object. That is why a static function cannot use per-object data directly.

Common mistakes

• Using this.member (dot) instead of this->member (arrow) — this is a pointer.
• Returning this instead of *this when you meant to return the object by reference.
• Expecting this to exist in a static member function.
• Overusing this-> where there is no name clash (it is optional then).

Summary

• this is a hidden pointer to the object a member function runs on.
• Use this->name to tell a member from a same-named parameter.
• Return *this to enable method chaining.
• this is a pointer, so use the arrow operator with it.
• Static member functions have no this pointer.