Scope Resolution Operator vs this pointer in C++
Last Updated :
28 Nov, 2021
Scope resolution operator is for accessing static or class members and this pointer is for accessing object members when there is a local variable with the same name.
Consider below C++ program:
CPP
#include <iostream>
using namespace std;
class Test {
int a;
public :
Test() { a = 1; }
void func( int a) { cout << a; }
};
int main()
{
Test obj;
int k = 3;
obj.func(k);
return 0;
}
|
Explanation: The output for the above program is 3 since the “a” passed as an argument to the func shadows the “a” of the class .i.e 1
Then how to output the class’s ‘a’. This is where this pointer comes in handy. A statement like cout <<this->a instead of cout << a can simply output the value 1 as this pointer points to the object from where func is called.
CPP
#include <iostream>
using namespace std;
class Test {
int a;
public :
Test() { a = 1; }
void func( int a) { cout << this ->a; }
};
int main()
{
Test obj;
int k = 3;
obj.func(k);
return 0;
}
|
How about Scope Resolution Operator?
We cannot use the scope resolution operator in the above example to print the object’s member ‘a’ because the scope resolution operator can only be used for a static data member (or class members). If we use the scope resolution operator in the above program we get compiler error and if we use this pointer in the below program, then also we get a compiler error.
CPP
#include <iostream>
using namespace std;
class Test {
static int a;
public :
void func( int a) { cout << Test::a; }
};
int Test::a = 1;
int main()
{
Test obj;
int k = 3;
obj.func(k);
return 0;
}
|
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