Thread: How to enable a choice for what type of object to create?

You have a scope problem. Variables declared in a block are destroyed once the block ends. Your if statements are a short hand notation for:

Code:

if(answer == 1)
{
	foo makeobject;
}
if(answer == 2)
{
	test makeobject;
}

Once a block ends, the objects declared therein cease to exist(unless the objects are dynamically allocated memory with the new operator, in which case they stay in existence until you delete them).

Also, you should consider how protected/private members are assigned values in a class.

Originally Posted by 7stud

You have a scope problem. Variables declared in a block are destroyed once the block ends. Your if statements are a short hand notation for:

Code:

if(answer == 1)
{
    foo makeobject;
}
if(answer == 2)
{
    test makeobject;
}

Once a block ends, the objects declared therein cease to exist(unless the objects are dynamically allocated memory with the new operator, in which case they stay in existence until you delete them).

That should do the trick I had not considered using new and delete.

Originally Posted by 7stud

Also, you should consider how protected/private members are assigned values in a class.

Thanks for the concern (not being sarcastic but sincere). It was just a quick example to reproduce my problem so I neglected to include any constructors. If this is not in regard to the constructor can you please explain?

Thank you very much for taking the time to help me 7stud.

If memory serves me correctly, you can do something like this:

Code:

int main()
{
       first* makeobject;
	std::cout << "Enter 1 for class foo and 2 for class test. " << std::endl;
	int answer = 0;
	std::cin >> answer;
	if(answer == 1)
		makeobject = new foo;
	if(answer == 2)
		makeobject = new test;
	makeobject.display();
                delete makeobject;
	return 0;
}

Whooooo guys, you've all overlooked the fact that first has no display() function
Revised:

Code:

#include <iostream>

class first
{
public:
	virtual void display();

protected:
	int variable1;
	int variable2;
};

class foo : public first
{
private:
	int variable3;

public:
	void display()
	{
	std::cout << variable1 << " " << variable2 << " " << variable3 << std::endl;
	}
};

class test : public first
{
private:
	int variable4;

public:
	void display()
	{
	std::cout << variable1 << " " << variable2 << " " << variable4 << std::endl;
	}
};

int main()
{
	std::cout << "Enter 1 for class foo and 2 for class test. " << std::endl;
	int answer = 0;
	std::cin >> answer;

	first* objectPtr;
	if(answer == 1)
		objectPtr = new foo;
	else if(answer == 2)
		objectPtr = new test;

	objectPtr->display();
	delete objectPtr;
	return 0;
}