Thread: Validity Check.

Greeting,

I wonder how can I improve my validity check for user input? I only want them to key in certain range of digit.

Also for my validity check, when I key in character such as ABC, it lead to infinity loop

Here is my code :

Code:

/*Write a program that can calculate user's age by getting user input their birth date.*/

#include "stdafx.h"
#include <iostream>
#include <time.h>


using namespace std;


int main()
{
	int yyyy, mm, dd; //year, month, day
	int i = 0; //for the sake of validity check


	// current date/time based on current system
	time_t t = time(0);
	tm *now = localtime(&t);


	/* Find a better way to validate user input
	 * "isDigit" should able to do the trick
	 * Bug : Key in character lead to infinity loop
	*/
	//Year
	do
	{
		cout << "Enter your birth date of Year:\n?";
		cin >> yyyy; //do checking
		if (yyyy > 1900 && yyyy < 2500) { //2500..? Lol
			i++; //i=1
		}
	} while(i == 0);


	//Month
	do
	{
		cout << "Enter your birth date of Month:\n?";
		cin >> mm; //do checking
		if (mm > 0 && mm < 13) { // 1 ~ 12
			i++; //i=2
	}
	} while(i == 1);


	//Day
	do
	{
		cout << "Enter your birth date of Date:\n?";
		cin >> dd; //do checking
		if (dd > 0 && dd < 32) { //I'm kind of lazy to check how many days in a month, well, 1 ~ 31
			i++; //i=3
	}
	} while(i == 2);
	/*End of user input*/


	//Think a way to improve this so those comment will not needed
	if (mm <= (now->tm_mon + 1)) { //if birthday month <= current month
		if (dd <= (now->tm_mday)) { //if birthday date <= current date
			cout << "Your age is: " << (1900 + now->tm_year) - yyyy << "years,"; //Already pass birthday
			cout << " " << ((now->tm_mon + 1) - mm) << "months,"; //1 has added into years
			cout << " and " << ((now->tm_mday) - dd) << "days" << endl; //and so the day
		} else {
			cout << "Your age is : " << (1900 + now->tm_year) - yyyy - 1 << "years,"; //Not yet pass birthday
			cout << " " << ((now->tm_mon + 1)) << "months,"; //just print how many months
			cout << " and " << ((now->tm_mday)) << "days" << endl; //and day you lived
		}
	} else {
		cout << "Your age is : " << (1900 + now->tm_year) - yyyy - 1 << "years,"; //Not yet pass birthday
		cout << " " << ((now->tm_mon + 1)) << "months,"; //just print how many months
		cout << " and " << ((now->tm_mday)) << "days" << endl; //and day you lived
	}
}

Regards,
Milo.

Originally Posted by grumpy

Look up the standard string class, create a std::string named (say) some_string, and then use std::getline(std::cin, some_string) to read a complete line of input. Check/parse the contents of some_string BEFORE trying to interpret it as a set of integers.


Alternatively, you could also check cin.fail(). That function will return true if an error occurs for the streaming operator (e.g. a character entered that cannot be interpreted as an int). You will then need to clear the failbit (cin.clear()), and then gobble a character from cin before attempting to use the streaming operator again. Bear in mind there are other errors that may affect a stream (eg end of file or loss of integrity of the stream).

Hi, thanks for your reply!
To be honest I still very fresh in C++ as I just started a few days ago, I'm sorry that I can't really understand what do you mean

Can you provide me some example code and do some further explanation on that?

Or is there any more simple way of doing the trick?

Thanks!

Regards,
Milo.