Thread: Pointer Question

Code:

employee * create()
{
	employee * _newemployee;
	string input1;
	string input2;
	cout << "Please enter the new employee's name: ";
	getline(cin, input1);
	cout << "Please enter the new employee's payrate: ";
	getline(cin, input2);
	_newemployee = new employee(input1, input2);
	return _newemployee;
}

Is this correct? I didn't get any errors or exceptions in debug. I'm just wondering if this is correct usage pf pointers? I had to check a tutorial and I haven't really programmed much in a long time, any feedback would be appreciated!

If the constructor is correct, then it could well be correct, though I might write:

Code:

employee* create()
{
    cout << "Please enter the new employee's name: ";
    string name;
    getline(cin, name);
    cout << "Please enter the new employee's payrate: ";
    string payrate;
    getline(cin, payrate);
    return new employee(name, payrate);
}

That said, do you really need to use new here?

I wanted to do new because eventually what I want to do is something like this:

Code:

int main()
{
	int selection;
	string input;
	bool goodinput = false;
    while (goodinput == false)
	{
		cout << "Welcome to the employee database, what would you like to do?" << endl		// prompt
			 << "1. Add an employee" << endl << "2. Modify an employee" << endl;

		getline(cin, input);	//get input
		stringstream(input) >> selection;	//extract selection integer

		if (selection == 1)
		{
			goodinput = true;
			employees.push_back(create());
		}
		else if (selection == 2)
		{
			goodinput = false;
		}
		else
		{
			goodinput = false;	// invalid selection - continue loop
			cout << "Please enter a valid selection, 1 or 2." << endl;
		}
	}
    return 0;
}

Also, if I explicitly call an instance of employee, like employee newemployee(name,payrate)...
Doesn't that instance only last for the scope of the function?
If not I don't need new at all, and I can just return a reference.

Originally Posted by Shamino

I wanted to do new because eventually what I want to do is something like this:

You could, but then you will need to do manual memory management, e.g., to delete what you new.

Originally Posted by Shamino

Also, if I explicitly call an instance of employee, like employee newemployee(name,payrate)...
Doesn't that instance only last for the scope of the function?

Yes, but you can return a copy, and if you are calling this function like:

Code:

employee x(create());

This copying may even be optimised away.

Originally Posted by Shamino

If not I don't need new at all, and I can just return a reference.

You should not return a reference to a local variable.

Would deleting the contents of the vector before the program shuts down cover my butt if I use new?

Or running a destructor for each employee held in the employees vector?

Oh good, then new is safe as long as I clean up after myself? I wanted to use pointers, because I know the stack is limited, and with a database potentially getting large I'd want to dynamically manage my memory eventually. I've done stuff like this before, it's just been so long I'm refamiliarizing myself with syntax.

Hmmm, it would save memory in the long haul to use polymorphism to differentiate between types of employees, for instance, salaried and hourly workers..

Then I wouldn't have a single employee structure that could possibly have unused variables, does this make sense?

Code:

employee* get_employee(string _name)
{
	for (unsigned int i = 0; i < employees.size();)
	{
		if (_name.compare(employees[i]->name) == 1)
		{
			return employees[i];
		}
		else
		{
			i++;
		}
	}
}

void list_employees(vector<employee*> * _employees)
{
	for (unsigned int i = 0; i < _employees->size(); i++)
	{
		cout << employees[i]->name << endl;
	}
}

Is this going to have the desired effect? My loop logic might be off.

I would write it as:

Code:

employee* get_employee(string _name)
{
    for (std::size_t i = 0; i < employees.size(); i++)
    {
        if (_name.compare(employees[i]->name) == 1)
            return employees[i];
    }
}
 
void list_employees(vector<employee*> & _employees)
{
    for (std::size_t i = 0; i < _employees.size(); i++)
    {
        cout << employees[i].name << endl;
    }
}

That said, what is this?
if (_name.compare(employees[i]->name) == 1)
How does your employee struct/class look like? I am skeptical.

Furthermore, if you intend to find an employee by name a lot, you may want to use a set, a map or a hash table for fast lookup.
Also, if you really must use pointers, then use smart pointers.