Thread: How can I?

Why I cannot use this methode to flush out the invalid input.
I wanted to have the input part inside the while loop, unlike the one the FAQ show on the board(Inside the while condition).

Code:

#include <iostream>
#include <cctype>
#include <fstream>
#include <limits>
using namespace std;
struct inventory_items
{
	int code,quantity,reorder_level;
	char name[100], units[100];
	double price;
};

int main()
{
	int counter=0;
	inventory_items s;

	while (counter==0)
	{
  
	  cout<<"Enter the item code.\n";
	  cin>>s.code;
	  cin.get();
	  if(!isdigit(s.code))
	  {
		cout << "\nInvalid input" <<endl;
		cin.clear();
		cin.ignore(std::numeric_limits < int >::max(), '\n');
	  }
	  else
	  {
		  cout<<"You enter : "<<s.code<<endl;
		  counter=1;
	  }
	}
  return 0;
}

Or, an easier way to read a whole number:

Code:

#include <iostream>
#include <cctype>
#include <fstream>
#include <limits>
using namespace std;
struct inventory_items
{
	int code,quantity,reorder_level;
	char name[100], units[100];
	double price;
};

int main()
{
	int counter=0;
	inventory_items s;

	while (counter==0)
	{
  
	  cout<<"Enter the item code.\n";
	  cin>>s.code;
	  if(!cin)
	  {
		cout << "\nInvalid input" <<endl;
		cin.clear();
		cin.ignore(std::numeric_limits < int >::max(), '\n');
	  }
	  else
	  {
		  cout<<"You entered : "<<s.code<<endl;
		  counter=1;
	  }
	}
  return 0;
}

One note, if someone enters "10254rgh", it is seen as a valid input of "10254". Also, you're always going to leave something in the input stream, so you may want to do the clear/ignore no matter what:

Code:

int main()
{
    int counter=0;
    inventory_items s;

    while (counter==0)
    {
  
      cout<<"Enter the item code.\n";
      cin>>s.code;
      if(!cin)
      {
        cout << "\nInvalid input" <<endl;
      }
      else
      {
          cout<<"You entered : "<<s.code<<endl;
          counter=1;
      }
      cin.clear();
      cin.ignore(std::numeric_limits < int >::max(), '\n');
    }
  return 0;
}