Can we initialize a reference variable with a pointer variable?

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C++

#include <stdio.h>
#include<iostream>
#include<cstring>
using namespace std;
class Base
{
    public:
        int a;
        Base():a(0){};
        Base(int x):a(x){};
        void geta(){
            cout<<"a="<<a<<endl;
        }
};
int main()
{
    Base b1(5);
    Base *b3 = &b1;
    Base &b2 = *b3;   //Is it okay?
    b2.geta();
    b3->geta();
    Base b4(10);
    b3 =  &b4;
    b2.geta();
    b3->geta();   
    return 0;
}

What I have tried:

The above Code compiles and gives desired output.
Output:
a=5
a=5
a=5
a=10
My questions:
1. Can we initialize a reference variable with a pointer variable?
2. If initializing of reference variable with pointer is allowed then when printing b2.geta(); and
b3->geta(); for the second time then both should have given the same value. Why they are different?

Posted 11-Oct-18 11:12am

GeekyMukesh

Updated 11-Oct-18 13:19pm

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User 59241 · Accepted Answer · 2018-10-11T13:19:00

Your question asks :

Quote:
Can we initialize a reference variable with a pointer variable?

Yes we can: your code demonstrates that.
The next thing is "

Quote:
both should have given the same value. Why they are different?

The output is correct. This is actually why we use pointers. Pointers - C++ Tutorials[^]

int main()
{
	Base b1(5);
	Base *b3 = &b1;   // Create pointer b3 and set to point to b1 b3->a==5
	Base &b2 = *b3;   // Create reference b2 and inititialize to whatever b3 points to which is b1 
	// NOTE at this line *b3 dereferences b3 which results in b1. If b3 did not point to a valid object (eg b3==NULL) this would cause the next line to fail at runtime

	b2.geta();
	b3->geta();

	Base b4(10);
	b3 = &b4;         // Now point b3 to b4 b3->a == 10
	cout << "a=" << b3->a << endl;
	b2.geta();
	b3->geta();
	return 0;
}

You set the pointer b3 to point to b1 but later you set it to point to b4. Thus the output is correct.
You can view what happens using your debubugger.