Thread: cin doesn't work after the first time

Code:

#include <iostream>
#include <conio.h>

using namespace std;

class publication
{
protected:
	char title[20];
	float price;
public:
	publication() : price(0.0)
	{
		title[0] = '\0';
	}

	virtual void getData()
	{
		cout<<"\nInput title: "; cin.get(title, 20);
		cout<<"\nInput price: "; cin>> price;
	}
	
	virtual void putData()
	{
		cout<<"\nTitle: "<< title;
		cout<<"\nPrice: "<< price;
	}
};

class book : public publication
{
private:
	int pages;
public:
	book() : publication(), pages(0)
	{	}

	void getData()
	{
		publication::getData();
		cout<<"\nInput pages: "; cin>> pages;
	}

	void putData()
	{
		publication::putData();
		cout<<"\nPages: "<< pages;
	}
};

class tape : public publication
{
private:
	int minutes;
public:
	tape() : publication(), minutes(0)
	{	}

	void getData()
	{
		publication::getData();
		cout<<"\nInput minutes: "; cin>> minutes;
	}

	void putData()
	{
		publication::putData();
		cout<<"\nMinutes: "<< minutes;
	}
};

int main()
{
	publication* ptr[10];
	int pubs = 0;
	int i;

	do
	{
		if (pubs < 10)
		{
			cout<<"\nChoose between a book or tape (b/t): ";

			if (_getche() == 'b')
				ptr[pubs] = new book;
			else
				ptr[pubs] = new tape;
			
			ptr[pubs]->getData();
			pubs++;

			cout<<"\nInput another? (y/n): ";
		}
		else
		{
			cout<<"\nSorry, out of room.";
			break;
		}
	}
	while(_getch() == 'y');

	for (i = 0; i < pubs; i++)
	{
		ptr[i]->putData();
	}

	cout<<"\n\n";
	system("Pause");

	for (i = 0; i < pubs; i++)
	{
		delete ptr[i];
	}

	return 0;
}

In the above program, the main loop loops through once successfully, but on subsequent times it's as if the cin calls in the different getData() functions don't exist. It cout's the correct text (Inupt title:, Input price, etc.) but it never allows the user to cin the data; it just moves on to the next cout.

Any ideas why this is happening?

What exactly is a trailing newline, and how does it come about?

I ran that code and I think I understand what a trailing newline is, but I still don't know where it's occurring in my program. I changed the main loop to this:

Code:

do
	{
		if (pubs < 10)
		{
			cout<<"\nChoose between a book or tape (b/t): ";

			if (_getche() == 'b')
				ptr[pubs] = new book;
			else
				ptr[pubs] = new tape;
			
			if (pubs > 0)
				cin.ignore();
			ptr[pubs]->getData();
			pubs++;

			cout<<"\nInput another? (y/n): ";
		}
		else
		{
			cout<<"\nSorry, out of room.";
			break;
		}
	}
	while(_getche() == 'y');

which fixes the problem, but I still have no idea where the trailing newline is. The last two inputs before ptr[pubs]->getData() are calls to _getche(), which don't even require the user to press enter. Is the trailing newline still from either book::getData() or tape::getData() the last time through the loop? I would think if this was the case it would affect _getche(), but it doesn't. Unless input with cin is handled completely separate from _getche()??? Or maybe I'm just completely misunderstanding what a trailing newline is in the first place.

Originally Posted by Elysia

Why use char? Use std::string and std::getline instead. Safe, no worries, and left over data (hopefully).
Also, why use pointers? You don't need them.
Furthermore, the class function names are misleading: get should be named set and put should be named get. And while we're at it, pass in the data to store via arguments and make separate get functions for retrieving them. Don't use std::cin inside the class; that hurts flexibility.

This is simply an example program testing out various concepts that I've learned recently. I'm sure there are more efficient ways to do things or better function names to use, but I'm not really concerned with this particular program being perfect.