getline(...) not pausing for user input

[Greywolfe1982]

I'm trying to write a function within my class that I can call within the program to write questions from the running program to a file. My problem is that when I call getline(...), it doesn't wait for a user input...sometimes. Here's what happens when I run the program: (Input 1, 2, and 3, and Y were inputs by me)

Would you like to enter a question? Y/N:
Y
Please enter the question.
Please enter answer #1
(pause for input)
Input 1
Is this the correct answer? Y/N
(pause for input)
Y
Please enter answer #2
Please enter answer #3
(pause for input)
Input 2
Please enter answer #4
Input 3
Press any key to continue...

The file after this looks like this:

Input 1

Input 2
Input 3
Input 1

(The blanks are intentionally there)


Note, the program I'm using them in just declares a class of that type and calls this function:

	void trivia::question_to_file()
	{
		bool corr=false;	// Used to ask user which answer is correct
		char user_input;	// Used to read user choice
		string temp, correct_answer;		// Used to temporarily store question/answers

		ofstream fout;

		fout.open("questions.txt");
		if(fout.fail())
		{
			cout << "There was an error opening the output file";
			exit(1);
		}

		cout << "Would you like to enter a question? Y/N:" << endl;
		cin >> user_input;
		
		while((toupper(user_input) != 'Y') && (toupper(user_input) != 'N'))
		{
			cout << "Invalid input. Please enter Y for yes, or N for no" << endl;
			cin >> user_input;
		}
		
		if(toupper(user_input) == 'N')
		{
			cout << "Returning to main menu" << endl;
			return;
		}

		if(toupper(user_input) == 'Y')
		{
			cout << "Please enter the question." << endl;
			getline(cin, temp, '\n');

			fout << temp << endl;

			for(int i=1; i<5; ++i)
			{
				cout << "Please enter answer #" << i << endl;
				getline(cin, temp, '\n');

				if(corr == false)
				{
					cout << "Is this the correct answer? Y/N" << endl;
					cin >> user_input;
					
					while(toupper(user_input) != 'Y' && toupper(user_input) != 'N')
					{
						cout << "Invalid input. Please enter Y for yes, or N for no" << endl;
						cin >> user_input;
					}
						
					if(toupper(user_input) == 'Y')
					{
						correct_answer = temp;
						corr = true;
					}
				}
			
				fout << temp << endl;
			}

			if(corr == false)
			{
				cout << "No correct answer was chosen. Using answer #4." << endl;
				fout << temp << endl;
			}
			else
			{
				fout << correct_answer << endl;
			}

		}

	}

Any help with why I'm skipping lines would be much appreciated. Thanks!

[1yR4jE8b]

I didn't compile or run your code, but I can tell just from looking that it is because you are mixing 'cin' with 'getline'. std::cin leaves the newline character in the buffer after pressing enter, and getline just grabs it and keeps going, that's why getline doesn't block to wait for input.

[Zhuge]

cin>> will leave newlines in the buffer when the user presses enter. getline() reads this as the user having pressed enter to "skip" the input.

You can use cin.ignore() to get rid of those extra characters before using getline().

[Greywolfe1982]

Thanks for the replies. It works...kinda. The code has been altered a bit. I added my for loop (which is able to write from the pre-loaded set of questions to the output file), and, following that, made the cin.ignore() changes (added it before I used getline(...)). I'm assuming there's something in the way I wrote it using ignore that is causing it to do this, but this is what happens:

In file initially
Question 1
Answer 1
Answer 2
Answer 3
Answer 4
Correct
Question 2
Answer 2 1
Answer 2 2
Answer 2 3
Answer 2 4
Correct answer 2


In file after input
Question 1
Answer 1
Answer 2
Answer 3
Answer 4
Correct
Question 2
Answer 2 1
Answer 2 2
Answer 2 3
Answer 2 4
Correct answer 2






Q1
A1
A2
A3
A4
A1


Input log
Would you like to enter a question? Y/N:
Y (enter)
Please enter the question.
Q2 (enter)
(enter)
Please enter answer #1
A1 (enter)
Is this the correct answer? Y/N
Y (enter)
Please enter answer #2
A2 (enter)
(enter)
Please enter answer #3
A3 (enter)
(enter)
Please enter answer #4
A4 (enter)
(enter)

I'm needing to hit enter before I write any of my questions/answers. In addition to this problem, I'm getting a set of blank spaces in my output (is it reading when I hit enter as a set of question/answers?) My apologies for the confusing, but I'm really not sure what's going on in here. Here's the code:

	void trivia::question_to_file()
	{
		bool corr=false;	// Used to ask user which answer is correct
		char user_input;	// Used to read user choice
		string temp, correct_answer;		// Used to temporarily store question/answers

		ofstream fout;

		fout.open("questions.txt");
		if(fout.fail())
		{
			cout << "There was an error opening the output file";
			exit(1);
		}

		for(size_t x = 0; x < questions.size(); ++x)
		{
			for(size_t i = 0; i<6; ++i)
			{
				fout << questions[x][i] << endl;
			}
		}

		cout << "Would you like to enter a question? Y/N:" << endl;
		cin >> user_input;
		
		while((toupper(user_input) != 'Y') && (toupper(user_input) != 'N'))
		{
			cout << "Invalid input. Please enter Y for yes, or N for no" << endl;
			cin >> user_input;
		}
		
		if(toupper(user_input) == 'N')
		{
			cout << "Returning to main menu" << endl;
			return;
		}

		if(toupper(user_input) == 'Y')
		{
			cin.ignore();
			cout << "Please enter the question." << endl;
			getline(cin, temp, '\n');

			fout << temp << endl;

			for(int i=1; i<5; ++i)
			{
				cin.ignore();
				cout << "Please enter answer #" << i << endl;
				getline(cin, temp, '\n');

				if(corr == false)
				{
					cout << "Is this the correct answer? Y/N" << endl;
					cin >> user_input;
					
					while(toupper(user_input) != 'Y' && toupper(user_input) != 'N')
					{
						cout << "Invalid input. Please enter Y for yes, or N for no" << endl;
						cin >> user_input;
					}
						
					if(toupper(user_input) == 'Y')
					{
						correct_answer = temp;
						corr = true;
					}
				}
			
				fout << temp << endl;
			}

			if(corr == false)
			{
				cout << "No correct answer was chosen. Using answer #4." << endl;
				fout << temp << endl;
			}
			else
			{
				fout << correct_answer << endl;
			}

		}

	}

[Greywolfe1982]

Bump

[coder777]

if you want to ignore new line you have to explicitly write that: cin.ignore(1000, '\n');

That's only necessary when there was a previous 'cin'. But should not do harm otherwise. So it might be best if you 'ignore' new line directly after 'cin' because it might affect the following 'cin'.

Not that I use that often though