Having issues with cin.getline and cin

[Catalyst8487]

In our final assignment for the year, we were given an assignment to create an array to structs that held information pertaining to students in a class. I have the program done essentially, but I'm getting a really annoying bug where with every loop past the first one, the program is "skipping over" inputting the students name for the 2nd, 3rd, 4th, etc... loops.

I believe I've isolated the problem to being something with cin.getline, and something about needing to clear the buffer after every loop. I can't seem to figure out how to clear the buffer.

Student.h

// Global constants
const int STUDENT_NAME = 41;	// Max number of characters for a students name
const int STUDENT_MAJOR = 41;	// Max number of characters for a students major
const int STUDENT_YEAR = 21;	// Max number of characters for a students year
const int STUDENT_ID = 5;

// Declaration of our Student Structure
struct Student
{
	char name[STUDENT_NAME];	// Stores full name of student
	char major[STUDENT_MAJOR];	// Stores major of student
	char year[STUDENT_YEAR];	// Stores year of student (Freshman, Sophomore, Junior, Senior)
	int studentID;				// Unique number to identify each student
	float GPA;					// Students Grade Point Average
};

// Declaration of our class
class myRoster
{
	public:
		void FillRoster (Student CourseRoster[], int classSize);
		float AverageGPA (Student CourseRoster[], int classSize);
		void OutputRoster (Student CourseRoster[], int classSize, char *pClassName, char *pClassNumber);
	private:
		struct myStruct
		{
			int a;
			int b;
			float c;
		};


		


};

Implementation.cpp

#include <iostream>
#include <iomanip>

#include "Student.h"

using namespace std;


// FillRoster will take each student in the class (in our case, 6) and
// populate their name, their major, their student ID, and their GPA.
void myRoster::FillRoster (Student CourseRoster[], int classSize)
{
	for (int i = 0; i < classSize; i++)
	{
		// Get Students Name
		cout << endl << "Enter the students name. > ";
		cin.getline(CourseRoster[i].name, STUDENT_NAME);
		cin.ignore(cin.rdbuf()->in_avail(), '40');
		
		// Get Students Major
		cout << endl << "Enter the students major. > ";
		cin.getline(CourseRoster[i].major, STUDENT_MAJOR);
		cin.ignore(cin.rdbuf()->in_avail(), '40');
		
		do
		{
			// Get Students Student ID. 
			CourseRoster[i].studentID = 10000;
			cout << endl << "Enter the students ID number (Between 10000 and 99999). > ";
			cin >> CourseRoster[i].studentID;
		}
		while (CourseRoster[i].studentID < 10000 || CourseRoster[i].studentID > 99999);
		
		do
		{
			// Get Student GPA
			cout << endl << "Enter the students GPA. > ";
			cin >> CourseRoster[i].GPA;
		}
		while (CourseRoster[i].GPA < 0.0 || CourseRoster[i].GPA > 4.0);		
	}
	return;
}


float myRoster::AverageGPA (Student CourseRoster[], int classSize)
{
	// Declare variable to hold the average GPA
	float avgGPA = 0.0;

	for (int j = 0; j < classSize; j++)
	{
		avgGPA = avgGPA + CourseRoster[j].GPA;
	}

	avgGPA = avgGPA / classSize;

	return avgGPA;
}


void myRoster::OutputRoster (Student CourseRoster[], int classSize, char *pClassName, char *pClassNumber)
{
	// Print out all the relevant information of the class and its students
	cout << endl << endl << "Roster for " << pClassName << ", Course ID " << pClassNumber << " is as follows: ";
	cout << endl << endl;
	cout << "NAME \t\t STUDENT ID \t\t ACADEMIC MAJOR \t GPA" << endl << endl;
	for (int k = 0; k < classSize; k++)
	{
		cout << CourseRoster[k].name << " \t\t " << CourseRoster[k].studentID << " \t\t\t "
			<< CourseRoster[k].major << " \t\t\t " << CourseRoster[k].GPA << endl;
	}


	return;
}

Main.cpp

#include <iostream>
#include <iomanip>

#include "Student.h"

using namespace std;

// Constants used througout the program
const int CLASS_SIZE = 2;	// Class/Roster size
const int CLASS_TITLE = 41;	// Max size of a class name.  Extra space for the NULL character.
const int CLASS_NUMBER = 9; // Max size of the class number name.  Extra space for the NULL character.

int main()
{
	// Create my strut object
	Student CourseRoster[CLASS_SIZE];

	// Create my class object 
	myRoster roster;

	// Create variables needed by the program.  className holds the name of the class,
	// classNumber holds the class abbreviation (CS115), avgGPA holds the average GPA
	// of the students in the class.  pAvgGPA is a pointer to avgGPA.
	char className[CLASS_TITLE];
	char classNumber[CLASS_NUMBER];

	char *pClassName = &className[0];
	char *pClassNumber = &classNumber[0];
	float *pAvgGPA = NULL;
		
	// Get the course name and course number from the user.  The cin.ignore lines 
	// ensure that we only take up to the maximum number of characters allowed by that 
	// field so that we don't accidentally try to create a course name with 60 
	// characters or a course number with 15 characters.
	cout << "Enter the name of the course. > ";
	cin.getline(className, CLASS_TITLE);
	cin.ignore(cin.rdbuf()->in_avail(), '40');

	cout << endl << "Enter the course number. > ";
	cin.getline(classNumber, CLASS_NUMBER);
	cin.ignore(cin.rdbuf()->in_avail(), '8');

	// Call the FillRoster Function
	roster.FillRoster(CourseRoster, CLASS_SIZE);

	// Calculate the Average GPA of the students
	cout << "The average GPA for the students in " << className << "is " 
		<< roster.AverageGPA(CourseRoster, CLASS_SIZE);

	// Output the class information
	roster.OutputRoster(CourseRoster, CLASS_SIZE, pClassName, pClassNumber);


	myRoster.myStruct.a = 1;

	system("pause");
	return 0;
}

Can anyone assist in fixing this annoying output issue?

[compuKidd]

I used to have lots of problem when using cin.getline, now Im not an expert with this kind of stuff but what we used to do to solve them is put a:

char enter[1];
cin.getline(enter,1);

after calls to cin>> (the operator >>()) cause as it seems cin>> leaves an enter when it reads from the stream so when cin.getline comes to read after cin>> it finds the enter and directly exit with nothing read, now putting the previous code after cin>> removes this enter and you can read whats after it. I can be a bit off about the details but I know this used (and still) to solve my problems with cin.getline, hope this was useful

btw what is:

cin.ignore(cin.rdbuf()->in_avail(), '40');