Unity 访问者模式（实例详解）

文章目录

- - 实例1：简单的形状与统计访客
  - 实例2：游戏对象组件访问者
  - 实例4：Unity场景对象遍历与清理访客
  - 实例5：角色行为树访问者

访问者模式（Visitor Pattern）在Unity中主要用于封装对一个对象结构中各个元素的操作，使得可以在不改变这些元素类的前提下增加新的操作。下面我将提供五个简化版的代码实例来说明如何在C#中为Unity项目实现访问者模式：

实例1：简单的形状与统计访客

// 抽象元素接口
public interface IShape
{void Accept(IVisitor visitor);
}// 具体元素类
public class Circle : IShape
{public float Radius { get; set; }public void Accept(IVisitor visitor){visitor.Visit(this);}
}public class Square : IShape
{public float SideLength { get; set; }public void Accept(IVisitor visitor){visitor.Visit(this);}
}// 访问者接口
public interface IVisitor
{void Visit(Circle circle);void Visit(Square square);
}// 具体访问者：面积计算器
public class AreaCalculator : IVisitor
{public float TotalArea { get; private set; }public void Visit(Circle circle){TotalArea += Mathf.PI * circle.Radius * circle.Radius;}public void Visit(Square square){TotalArea += square.SideLength * square.SideLength;}
}// 使用示例
public class ShapeExample : MonoBehaviour
{public List<IShape> shapes;void Start(){IVisitor areaVisitor = new AreaCalculator();foreach (var shape in shapes){shape.Accept(areaVisitor);}Debug.Log("Total area: " + areaVisitor.TotalArea);}
}

实例2：游戏对象组件访问者

// 抽象游戏对象组件接口
public interface IGameObjectComponent
{void Accept(IGameObjectVisitor visitor);
}// 具体游戏对象组件
public class TransformComponent : IGameObjectComponent
{public Vector3 Position { get; set; }public void Accept(IGameObjectVisitor visitor){visitor.VisitTransform(this);}
}public class RenderComponent : IGameObjectComponent
{public Material Material { get; set; }public void Accept(IGameObjectVisitor visitor){visitor.VisitRender(this);}
}// 访问者接口
public interface IGameObjectVisitor
{void VisitTransform(TransformComponent component);void VisitRender(RenderComponent component);
}// 具体访问者：序列化器
public class GameObjectSerializer : IGameObjectVisitor
{public void VisitTransform(TransformComponent component){// 序列化Transform组件数据}public void VisitRender(RenderComponent component){// 序列化渲染组件数据}
}// 使用示例
public class GameObjectManager : MonoBehaviour
{public GameObject targetObject;void SerializeComponents(){IGameObjectVisitor serializer = new GameObjectSerializer();foreach (var component in targetObject.GetComponents<IGameObjectComponent>()){component.Accept(serializer);}}
}// ... 更多具体访问者的实现 ...

实例4：Unity场景对象遍历与清理访客

// 抽象游戏对象接口，扩展自MonoBehaviour以适应Unity环境
public interface ISceneGameObject : MonoBehaviour
{void Accept(ISceneVisitor visitor);
}// 具体的游戏对象类
public class GameObjectWithComponents : MonoBehaviour, ISceneGameObject
{public Transform MyTransform;public MeshRenderer Renderer;// 接受访问者public void Accept(ISceneVisitor visitor){visitor.Visit(this);}
}// 访问者接口
public interface ISceneVisitor
{void Visit(GameObjectWithComponents gameObject);
}// 清理访客：销毁无用的MeshRenderer
public class UnusedRendererCleaner : ISceneVisitor
{void Visit(GameObjectWithComponents gameObject){if (gameObject.Renderer == null || !gameObject.Renderer.enabled){GameObject.Destroy(gameObject.Renderer);}}
}// 使用示例
public class SceneManager : MonoBehaviour
{public List<ISceneGameObject> sceneObjects;void Start(){ISceneVisitor cleaner = new UnusedRendererCleaner();foreach (var obj in sceneObjects){obj.Accept(cleaner);}}
}// ... 更多具体访问者的实现 ...

实例5：角色行为树访问者

// 抽象行为节点接口
public interface IBehaviorTreeNode
{void Accept(BehaviorTreeVisitor visitor);bool Evaluate();
}// 具体的行为节点
public class MoveToTargetNode : IBehaviorTreeNode
{public Transform Target;public float DistanceThreshold;public void Accept(BehaviorTreeVisitor visitor) => visitor.VisitMoveToTarget(this);public bool Evaluate() => Vector3.Distance(transform.position, Target.position) > DistanceThreshold;
}public class AttackEnemyNode : IBehaviorTreeNode
{public Transform Enemy;public void Accept(BehaviorTreeVisitor visitor) => visitor.VisitAttackEnemy(this);public bool Evaluate() => Enemy != null && Enemy.gameObject.activeSelf;// 其他评估条件...
}// 访问者接口
public interface BehaviorTreeVisitor
{void VisitMoveToTarget(MoveToTargetNode node);void VisitAttackEnemy(AttackEnemyNode node);// 更多行为节点类型...
}// 具体访问者：AI逻辑执行器
public class AIExecutor : BehaviorTreeVisitor
{void VisitMoveToTarget(MoveToTargetNode node){// 执行移动到目标的行为逻辑}void VisitAttackEnemy(AttackEnemyNode node){// 执行攻击敌人的行为逻辑}// 其他行为节点的处理方法...
}// 使用示例
public class CharacterAI : MonoBehaviour
{public IBehaviorTreeNode rootNode;void Update(){var executor = new AIExecutor();rootNode.Accept(executor);if (rootNode.Evaluate()){// 根据行为树执行相应动作}}
}