Getting error : vector iterator incompatible

Question

I am making a program for class that manages a Hotel. I am able to successfully check-in a customer into a room. But when I try to check-out a customer from a room, I get a run-time error: vector iterator incompatible. I ran the debugger, and says the problem is in the condition statement of my while loop, but I cant figure out what the problem is (I think I used the debugger correctly). I tried looking at other post with this similar error but I was not able to find a solution. Can anyone help?

void Customer::removeRoomID(int rID)
{
    vector<int>::iterator iter;
    iter = roomsCheckedInto.begin();
    while(iter != roomsCheckedInto.end())   // <--DEBUGGER SAYS ERROR IN THIS LINE - ERROR: VECTOR ITERATOR INCOMPATIBLE
    {
        if(*iter==rID)
        {
            roomsCheckedInto.erase(iter);
        }
    }
}

Answer 1

std::vector iterators are invalidated once an erase operation has been performed. (See reference here)

Try changing your code to:

void Customer::removeRoomID(int rID)
{
   vector<int>::iterator iter;
   iter = roomsCheckedInto.begin();
   while(iter != roomsCheckedInto.end())   
   {
       if(*iter==rID)
       {
           // iter should now be set to the value
           // returned from the erase() method.
           iter = roomsCheckedInto.erase(iter);
       }
       else
       {
          ++iter;
       }
   }
}

Answer 2

You are not advancing your iterator anywhere.

You need to do ++iter at some point or your while loop will be endless.

Also don't forget .erase invalidates the iterator, so you can't simply advance after erase. Do iter = roomsCheckedInto.erase(iter); in case of matching id.