How to create an object without calling the same class constructor?

Question

4.50/5 (2 votes)

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I want to create an object that should not call my constructor..

C++

#include<iostream>
#include<conio.h>
using namespace std;
class me
{
public:
	me()
	{
cout<<"hi";
	}
	void fun()
	{
		cout<<"\nfun"<<endl;
	}
};
void main()
{
me b;
b.fun();
getch();
}

output:

hi
fun

My expected output is:

fun

What changes i have to make in that program to bring expected output..
The task is to create an object of that class and that should not call the constructor..

Posted 19-Oct-12 3:10am

J.Surjith Kumar

Updated 19-Oct-12 3:19am

CPallini

v2

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Comments

Argonia 19-Oct-12 9:16am

well you can create another constructor with params that doesn't do anything or at least doesn't print anything.As far as i know when you create an object from a class depending on how you create it always the classes constructor is called. Even if you don't declare your own one the compiler adds one with no params(default constructor).My point is when you create object a constructor is always called :)

Richard MacCutchan 19-Oct-12 9:47am

Remove the cout statement from the constructor.

3 solutions

Solution 1

Short answer: You cannot do that.
Longer answer: You cannot do that, is there any reason why do you want to do that?

Posted 19-Oct-12 3:23am

CPallini

Comments

J.Surjith Kumar 19-Oct-12 9:58am

I got this question in the interview and they told that there is a technique to solve this.

Solution 2

Every class is required to have a constructor. You are not required to have it do anything useful. Write an empty constructor and move on.

Posted 19-Oct-12 3:38am

Chuck O'Toole

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Orjan Westin · Accepted Answer · 2012-10-19T04:18:00

Short answer: you cannot do that.

Cheating answer: make fun() static

C++

class me
{
public:
  me()
  {
    cout<<"hi";
  }
  static void fun()
  {
    cout<<"\nfun"<<endl;
  }
};
void main()
{
  b::fun();
  getch();
}

Dangerous, cheating answer: don't call the constructor

C++

void main()
{
  me* b = 0;
  b->fun();
}

This works, in this example, because the me class has no member data and no virtual functions (so no virtual function table as implicit member data). If I ever saw anyone submit code like this, I'd recommend they were sacked.

In an interview, they might have been interested in seeing if you had the understanding required to find this 'solution', and to say "In this case it would work, but I wouldn't do it for real".