C++ this pointer
'this' is a pointer that points to the object for which this function was called. The 'this' pointer holds the memory address of the current object. The 'this' pointer is implicitly passed to a member function when it is called.
Consider the following simple example:
The variable 'id' can be used directly inside a member function, as
The above initialization statement can be written using 'this' pointer, as
C++ internally use the initialization of id=10; as this->id=10;
Another key feature of the 'this' pointer is to return the object on which it is pointing. For example
The above statement inside member function returns the object which is invoking the member function.
Output:
Output:
class Student{
int id;
.....
.....
};
id=10;
this->id=10;
return *this;
C++ 'this' Example 1
#include<iostream>
using namespace std;
class Student
{
private:
int id;
public:
void setId (int id)
{
this->id = id; //retrieve the object's 'id' hidden by the private
variable 'id'
}
void printId() { cout << "id = " << id << endl; }
};
int main()
{
Student obj;
int id = 10;
obj.setId(id);
obj.printId();
return 0;
}
id=10
C++ 'return *this' Example 2
#include<iostream>
#include<cstring>
using namespace std;
class student
{
private:
char name[20];
int mark;
public:
student(char *n, int m){
strcpy(name,n);
mark = m;
}
student greater(student & a){
if(a.mark>=mark){
return a; //return when s1.greater(s2); is call
}
else{
return *this; //return when s1.greater(s3); is call
}
}
void display(void){
cout<< "Name: "<<name<<endl<<"Mark: "<<mark<<endl;
}
};
int main()
{
student s1("Ajay",70);
student s2("Lucky",60);
student s3("Raj",80);
student s = s1.greater(s2);
cout<< "Greater mark: "<<endl;
s.display();
s = s1.greater(s3);
cout<< "Greater mark: "<<endl;
s.display();
return 0;
}
Greater mark: Name: Ajay Mark: 70 Greater mark: Name: Raj Mark: 80