Bowling Game: State Machine: Std::Variant: Step 21

To make the “single strike, single spare and a bonus roll of 1” test work, we need to add a line similar to WaitingForSecondRollWith0Bonuses:

        class WaitingForSecondRollWith1Bonus
        {
            int first;
            int sumOfRolls(int pins) const { return first + pins; }
            bool isSpare  (int pins) const { return sumOfRolls(pins) == 10; }
        public:
            WaitingForSecondRollWith1Bonus(int first) : first(first) {}
            State Update(int pins, int& score, int& frame) const
            {
                score += pins*2;
                ++frame;
                if (isSpare(pins))  return WaitingForFirstRollWith1Bonus{};
                                    return WaitingForFirstRollWith0Bonuses{};
            }
        };

I added the check for isSpare(pins) and if it’s true, we return to WaitingForFirstRollWith1Bonus.

I see a ton of commonality with the WaitingForSecondRollWith0Bonuses class. Let’s extract a base class, derive both of these classes from it, and then click next.