Why do I need to press Enter twice after getline()? - c++

Question

Everything is working fine in this program except when it reaches getline() after cout<<"From Date: ";. At this point no matter if I give input or simply hit enter without input, I have to hit enter twice to proceed further. I tried removing cin.ignore() but it causes more problem by jumping over the first getline(). Here is the snippet which is causing this problem-
int main() {
Date d1;
int choice;
cout << "\nEnter choice: ";
cin >> choice;
cin.ignore(numeric_limits < streamsize > ::max(), '\n');
switch (choice) {
case 1:
d1.diffbw();
break;
default:
cout << "Wrong choice";
}
return 0;
}
void Date::diffbw() {
Date current, ref;
string choice;
cout << "\n Type 'man' to enter date manually else hit Enter to insert current date!";
do {
cout << "From Date:";
getline(cin, choice);
if (choice == "man")
current.getdate(); //getdate() assigns day, month and year in object current
else if (choice.empty())
current = sysDate(); //sysDate returns system date
else {
cout << "\n Wrong Choice!";
cout << "\n Enter Again?(y/n): ";
getline(cin, choice);
}
} while (choice == "y" || choice == "Y");
do {
cout << "To Date:";
getline(cin, choice);
if (choice.empty())
ref = sysDate();
else if (choice == "man")
ref.getdate();
else {
cout << "\n Wrong Choice!";
cout << "\n Enter Again?(y/n): ";
getline(cin, choice);
}
} while (choice == "y" || choice == "Y");
current.calcAge(ref); //calcAge() calculates difference between two given dates.
cout << "\n Difference: ";
cout << abs(current.day) << " day(s) " << abs(current.month) << " month(s) " << abs(current.year) << " year(s)";
}
P.S.- I am using g++ compiler on windows.
Edit: I posted the whole function here as many people are having difficulty in understanding the context here. I also corrected the 'cin.ignore()' syntax as suggested by #john. I am trying to calculate difference between two given dates.
The second 'do while' loop works without any bug although it is completely synonymous with the first one.

Answer 1

It might be because you are first trying to get a value by calling cin.getline() and afterwards the program is done but is waiting for confirmation and it gets the confirmation by you pressing enter.
Basically
Enter Value: 5 //Presses enter
Press any key to exit window.

Answer 2

Your statement
cout<<"\n\n From Date:";
is strange and probably wrong, since the std::cout stream is generally buffered.
You should use std::cout << "From date:" << std::endl; and read a good C++ programming book and check in this C++ reference that you are correctly using every function or feature from the C++ standard library.
If you compile with a recent GCC, I recommend enabling all warnings and debug info, so compiling with g++ -Wall -Wextra -g. Then use your debugger, e.g. GDB.
If your computer runs some Linux or POSIX system, you could be interested in using GNU readline: then the input line becomes user-editable. You might also want to code a graphical application with Qt.
Everything is working fine in this program
How did you check that? What debugger did you use? What test cases do you have? Did you try to type something with spaces, e.g. today's date as the user input? What did happen?

Answer 3

I slightly modified your program to avoid relying on the Date class, which you did not define:
#include <string>
#include <iostream>
#include <limits>
#include <math.h>
#include <stdio.h>
using namespace std;
void diffbw();
int main() {
int choice;
cout << "\nEnter choice: ";
cin >> choice;
cin.ignore(numeric_limits < streamsize > ::max(), '\n');
switch (choice) {
case 1:
diffbw();
break;
default:
cout << "Wrong choice";
}
}
void diffbw() {
string choice;
cout << "\n Type 'man' to enter date manually else hit Enter to insert current date!";
do {
cout << "From Date:";
getline(cin, choice);
cout << "choice";
if (choice == "man") {
}
else if (choice.empty()) {
}
else {
cout << "\n Wrong Choice!";
cout << "\n Enter Again?(y/n): ";
getline(cin, choice);
}
} while (choice == "y" || choice == "Y");
do {
cout << "To Date:";
getline(cin, choice);
if (choice.empty()) {
}
else if (choice == "man") {
}
else {
cout << "\n Wrong Choice!";
cout << "\n Enter Again?(y/n): ";
getline(cin, choice);
}
} while (choice == "y" || choice == "Y");
cout << "\n Difference: ";
}
and I don't see the same phenomenon you describe. That is, I don't need to press Enter twice. Please consider making your problematic program more minimal, and at the same time complete.