user enters String instead of Int [closed] - c++

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We have tried to search this problem but we haven't found any answers. If The user inputs a string variable when the system requires a integer how do you evade the problem with out using a while loop?
{
int grade_var=0,grade_1=0,sum=0;
cout<<"Enter the number of grades you have:\t";
cin>>grade_var;
for(int i=1;i<=grade_var;i++)
I don't wish to do a while loop for my program has a lot of integer insertions and want to know an easier way to correct rather than while loops?

Answer 1

While loops are generally the way to go.
However, to keep the code clean, you may want to consider putting said while loop into a helper function, so you can just call PollForIntegerInput(string prompt) from anywhere in your code, and then handle that input in one place. There is almost never a reason you should be duplicating an input loop like that.
As for a truly nonlooping answer, I have none.

Answer 2

Calling operator>> on a stream returns the stream itself, which can be converted to bool to check if the stream is in a good state. If a bad extraction happens, the stream is not in a good state. So you can do something like this:
if (cin >> grade_var)
This will check that it was successful. You can just negate the condition to find it if it wasn't successful. How you handle this condition is up to. Maybe you'll return early on failure. If you want to reprompt the user for correct input, however, you'll need a loop.

Answer 3

It's not too clear what your problem is, but...
It's almost always poor design to input the number of data
points which will follow. If you expect a series of int, for
example:
std::vector<int> grades;
int grade;
while ( std::cin >> grade ) {
grades.push_back( grade );
}
It doesn't get much simpler.
If you do want to insist on an exact number of input, outputting
an error when the user inputs something incorrect, the usual
pattern would be:
std::vector<int> grades;
while ( grades.size() != targetNumber ) {
int grade;
while ( !(std::cin >> grade) ) {
std::cout << "Integer wanted" << std::endl;
std::cin.clear();
std::cin.ignore( INT_MAX, '\n' );
}
grades.push_back( grade );
}
Still no for. (In fact, for loops with input are very, very
rare.)