converting a string to an integer (problem)

[Hirokachi]

In a project that I was working on, I was required to convert a string into a integer. I got this problem were whatever I input it will not accept as valid input.

Here is the problem code:

do
	{
		ss.flush();
		ss.clear();
		std::cout<< "Please type in your employees hours they worked for the first day:\n";
		std::getline (std::cin, temp);

		ss<< temp;

		ss>> E.hours;
		if (!ss.good())
		{
			std::cout<< "You have typed in something that is not a integer,\n" 
				"or you did and put stuff after it.\n";
		}
	} while(!ss.good());

E.hours is the type integer.

[TheMassiveChipmunk]

//How to use stringstreams 
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main ()
{
    string UserInput;
    int FinalVal;
    cout << "Please enter a number" << endl;
    getline (cin , UserInput);
    stringstream (UserInput) >> FinalVal;
    cout << "You entered " << FinalVal << endl;
    cin.get ();
    return 0;
}

I could not help you with the existing code because you did not show the whole program.
This should give you this:

Please enter a number
10
You entered 10

[Duthomhas]

Validating numeric inputs
http://www.cplusplus.com/forum/beginner/15655/#msg77321
http://www.cplusplus.com/forum/beginner/13044/#msg62827

[TheMassiveChipmunk]

Oh sorry let me rewrite my code :)

#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main ()
{
	string UserInput;
	int FinalVal;
	cout << "Please enter a number." << endl;
	while (true)
	{
		getline (cin , UserInput);
		UserInput.erase (UserInput.find_last_not_of (" \t") + 1);
		istringstream MyStream (UserInput);
		MyStream >> FinalVal;
		if (MyStream.eof ())
		{
			break;
		}
		cout << "The value you entered was not a number." << endl;
	}
	cout << "Okay you entered a number and it was " << FinalVal << endl;
	cout << "Press ENTER to end the program." << endl;
	cin.get ();
	return 0;
}

That is now this:
By the way thanks Duoas for the great post

Please enter a number.
Number
The value you entered was not a number.
4
Okay you entered a number and it was 4
Press ENTER to end the program.

[Hirokachi]

That fixed my problem.

Thanks Duoas and TheMassiveChipmunk!

[Hirokachi]

Apparently stringstream.flush does not work all the time. I ran this code:

void create_employees (std::vector<employee>& employees)
{
	employee E;
	std::string temp;
	std::stringstream ss;
	std::string answer = "yes";
	E.id = 0;
...
		do
		{
			ss.flush();
			ss.clear();
			std::cout<< "Please type in your employees hours they worked for the first day:\n";
			std::getline (std::cin, temp);
		
			temp.erase (temp.find_last_not_of (" \t") + 1);
			ss<< temp;

			ss>> E.hours;
			if (!ss.eof())
			{
				std::cout<< "You didn't type a number or you did and put something after it.\n";
			}
		} while(!ss.eof());

And I found that when I type a number the first time it works. But if i type argle then a number then it doesn't work. Can anybody tell me what is going on here?

[Duthomhas]

Yes, you are abusing the stringstream... they weren't really designed to be able to handle reuse that way. Instead, create a new one in each iteration of the loop:

	while (true)
	{
		std::cout << "Please type in ...";

		string s;
		std::getline (std::cin, s);
		s.erase (s.find_last_not_of (" \t") + 1);

		istringstream ss (s);
		ss >> E.hours;
		if (ss.eof()) break;  // only escape on valid input!

		std::cout << "Try again...";
	}

Hope this helps.

[Hirokachi]

Thanks again for the help.

I had no idea that I was abusing it.