游戏设计模式10-序列模式-更新方法

序列模式-更新方法

参考章节：https://gpp.tkchu.me/update-method.html

脑内画面

更新方法把"每帧要做的事情"分散到每个对象自己身上。游戏世界像一支队伍，主循环每帧点名，每个对象向前走一步。
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World.Update(dt)
Player.Update
Projectile.Update
Enemy.Update
Effect.Update

它解决的问题

游戏里大量对象都有跨帧行为：移动、冷却、动画、生命周期、AI。更新方法让对象把自己的时间推进逻辑封装起来，主循环只负责统一调度。

C# 示例

csharp 复制代码

public interface IUpdatable
{
    bool IsAlive { get; }
    void Update(float dt, GameWorld world);
}

public sealed class GameWorld
{
    private readonly List<IUpdatable> _objects = new();
    private readonly List<IUpdatable> _pendingAdd = new();

    public void Add(IUpdatable obj)
    {
        _pendingAdd.Add(obj);
    }

    public void Update(float dt)
    {
        foreach (var obj in _objects)
        {
            obj.Update(dt, this);
        }

        _objects.RemoveAll(obj => !obj.IsAlive);
        _objects.AddRange(_pendingAdd);
        _pendingAdd.Clear();
    }
}

public sealed class Projectile : IUpdatable
{
    private float _x;
    private float _speed;
    private float _life;

    public bool IsAlive => _life > 0f;

    public Projectile(float x, float speed, float life)
    {
        _x = x;
        _speed = speed;
        _life = life;
    }

    public void Update(float dt, GameWorld world)
    {
        _x += _speed * dt;
        _life -= dt;
    }
}

什么时候用

对象行为需要跨帧持续推进。
主循环不应该知道每种对象的细节。
对象数量和类型经常变化。

使用时的锋利边

更新顺序会影响结果。对象 A 先更新还是对象 B 先更新，可能改变碰撞、AI 感知或触发事件的结果。需要确定性时，要明确排序规则。

更新列表遍历时不要直接增删当前集合。使用延迟添加、死亡标记或命令队列，可以避免迭代器失效和跳过对象。