介紹
將訊息從發送方與接收方間解耦。

以下範例取自Game Programming Patterns一書。

C++範例片段

// 播放音效的資訊
struct PlayMessage
{
    SoundId id;
    int volume;
};

class Audio
{
public:
    static void Init()
    {
        m_head = 0;
        m_tail = 0;
    }

    // 將要播放的音效資訊加入列隊
    void Audio::playSound(SoundId id, int volume)
    {
        assert((m_tail + 1) % MAX_PENDING != m_head);

        // Add to the end of the list.
        m_pending[m_tail].id = id;
        m_pending[m_tail].volume = volume;
        m_tail = (m_tail + 1) % MAX_PENDING; // ring buffer
    }

    // 播放列隊中的音效
    void Audio::update()
    {
        // If there are no pending requests, do nothing.
        if (m_head == m_tail)
            return;

        ResourceId resource = loadSound(m_pending[m_head].id);
        int channel = findOpenChannel();
        if (channel == -1)
            return;
        startSound(resource, channel, m_pending[m_head].volume);

        m_head = (m_head + 1) % MAX_PENDING; // ring buffer
    }

private:
    static const int MAX_PENDING = 16;
    static PlayMessage m_pending[MAX_PENDING];
    static int m_head;
    static int m_tail;
};

Ref:
https://gameprogrammingpatterns.com/event-queue.html