So, I'm creating a connect4 game on the win32 console using C++, and... success! it works! my first game that I have written entirely myself, woop. The only problem is that it requires inputting numbers to cin at various intervals, and I have noticed that if you were to accidentally type a character instead of a number, it all goes tits up and loops the messages "Please enter your choice: " and "Sorry, that is not a valid choice" for thousands, maybe even millions of times if you were to let it.

Anyway as a result I've got a couple of questions - is there any way to avoid this problem? For example, is there a library function to validate whether whatever std::cin takes is an integer or not? I've got default cases and tried while/for loops but it doesn't seem to solve the problem.

Secondly, what's the best thing to do when I come into problems like this that stem from not knowing the capabilities of a library? I don't want to rely on gamedev.net and google all my life, however helpful they are!

Thanks in advance for any replies


int someVal;

while(!(cin >> someVal)) {
cin.reset();
cout << "Invalid value, try again.";
}

http://stackoverflow...numeric-input-c

Thanks for the response guys.

@UltimaX: Visual C++ doesn't seem to recognise the function cin.reset(), does it require a particular header file? As I'm using <iostream>


int getChoice()
{
int box = 0;
while ( (box != 1) && (box != 2) && (box != 3) && (box != 4) &&
(box != 5) && (box != 6) && (box != 7))
{
cout<<"\nPick a column (1 to 7) : ";
cin>>box;
}
return box;
}


this is the function I have written for getting a player's choice. Say you accidentally enter 'q' instead of '1', it will repeat "Pick a column (1 to 7) : " for thousands of times.

I think

Ignore

is what you were wanting to do.

Thanks for the replies everyone. Had a bit of trouble using 'ignore' and was confused by the other posts so I let it be for a while. Since then, I've got the book 'Accelerated C++' as seen it recommended here and on amazon, and after reading first few chapters learnt a lot, so can't recommend this enough to someone like me that's just starting out, seems to really explain the std library better and in more depth than anything i've used so far. With reference to the original problem though, I didn't know you could use "cin>>x" as a condition, and so whilst i'm still not sure how it converts that expression into a bool, i've used it and it works!

I didn't know you could use "cin>>x" as a condition, and so whilst i'm still not sure how it converts that expression into a bool, i've used it and it works!

operator>>() returns a reference to the input stream (to facilitate operator chaining, among other things). One of the stream base classes in turn includes an operator that allows for implicit conversion to 'bool', where the return value is determined by the current state of the stream's flags (basically, whether the stream is 'ok' or not). So when you write:

if (std::cin >> x)
operator>>() is invoked, a reference to std::cin is returned, the compiler tries to convert this return value to type 'bool', and is able to do so because of the conversion operator. The end effect is that the conditional basically checks to see if the state of the stream is still 'ok' after the extraction is attempted.

(IINM at least; I'm not looking at the documentation right now, so I can't guarantee I got all the details right.)