Bowling Game: State Machine: Unique_Ptr: Step 12

Ok, to pass the spare test, we need to make a few changes. First, to the Scorer class:

    class Scorer
    {
        bool bonusRoll = false;
        int score = 0;
    public:
        void AddRoll(int pins)
        {
            score += pins;
            if (bonusRoll) {
                score += pins;
                bonusRoll = false;
            }
        }
        void AddSpare(int pins)
        {
            score += pins;
            bonusRoll = true;
        }
        int Score() const { return score; }
    };

And to the two concrete State classes:

    struct WaitingForFirstRoll : public State
    {
        std::unique_ptr<State> Update(Scorer& scorer, int pins) const override
        {
            scorer.AddRoll(pins);
            return std::make_unique<WaitingForSecondRoll>(pins);
        }
    };
    class WaitingForSecondRoll : public State
    {
        int firstRoll;
    public:
        WaitingForSecondRoll(int firstRoll) : firstRoll(firstRoll) {}
        std::unique_ptr<State> Update(Scorer& scorer, int pins) const override
        {
            if (firstRoll + pins == 10) // spare!
                scorer.AddSpare(pins);
            else
                scorer.AddRoll(pins);
            return std::make_unique<WaitingForFirstRoll>();
        }
    };

We hold onto the firstRoll so that we can check if it’s a spare, in the WaitingForSecondRoll class. And that class must be constructed right in the WaitingForFirstRoll class.

In addition, we added an AddSpare method to the Scorer class, which sets a bool to true to tell us to add the bonus in on whatever the next roll is.

The comment // spare! is a hint that maybe we should refactor the code to make it clearer, but I’d hate to make this class bigger just to hold an explanatory method that’s only called once. Maybe we should add that later, if it ever gets called again from somewhere else; or maybe it should go on the Game class, so that other class can call it, too. But in any case, let’s wait on that.

Instead, let’s write another test, an “all spares” test.

When you’ve written that, click next.