In C++, can you manually set the failbit of a stream? How?

c++ validation inputstream
Jared picture Jared · Oct 28, 2009 · Viewed 12.2k times · Source

I am overloading the input stream operator for use with a Time class and would like to manually set the failbit of the input stream if the input doesn't match my expected time format (hh:mm). Can this be done? How?

Thanks!

Answer

Jack Lloyd picture Jack Lloyd · Oct 28, 2009

Yes, you can set it with ios::setstate, like so:

#include <iostream>
#include <ios>

int main()
   {
   std::cout << "Hi\n";

   std::cout.setstate(std::ios::failbit);

   std::cout << "Fail!\n";
   }

The second output will not be produced because cout is in the failed state.

(An exception seems cleaner to me, but YMMV)

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