【Unity与23种设计模式】访问者模式（Visitor）

GoF中定义：

“定义一个能够在一个对象结构中对于所有元素执行的操作。访问者让你可以定义一个新的操作，而不必更改到被操作元素的类接口。”

暂时没有完全搞明白

直接上代码

//访问者接口
public abstract class IShapeVisitor {
    public virtual void VisitSphere(Sphere theShpere) { }
    public virtual void VisitCube(Cube theCube) { }
    public virtual void VisitCylinder(Cylinder theCylinder) { }
}

//形状容器
public class ShapeContainer {
    List<IShape> m_Shapes = new List<IShape>();

    public ShapeContainer() { }

    public void AddShape(IShape theShape) {
        m_Shapes.Add(theShape);
    }

    public void RunVisitor(IShapeVisitor theVisitor) {
        foreach (IShape theShape in m_Shapes) {
            theShape.RunVisitor(theVisitor);
        }
    }
}

//形状的定义
public abstract class IShape {
    public abstract void RunVisitor(IShapeVisitor theVisitor);
}

//各形状的重新实现
public class Sphere : IShape {
    public override void RunVisitor(IShapeVisitor theVisitor)
    {
        theVisitor.VisitSphere(this);
    }
}

public class Cube : IShape {
    public override void RunVisitor(IShapeVisitor theVisitor)
    {
        theVisitor.VisitCube(this);
    }
}

public class Cylinder : IShape {
    public override void RunVisitor(IShapeVisitor theVisitor)
    {
        theVisitor.VisitCylinder(this);
    }
}

//绘图功能的Visitor
public class DrawVisitor : IShapeVisitor {
    public override void VisitSphere(Sphere theShpere)
    {
        base.VisitSphere(theShpere);
        Debug.Log("画Sphere");
    }

    public override void VisitCube(Cube theCube)
    {
        base.VisitCube(theCube);
        Debug.Log("画Cube");
    }

    public override void VisitCylinder(Cylinder theCylinder)
    {
        base.VisitCylinder(theCylinder);
        Debug.Log("画Cylinder");
    }
}

//测试类
public class TestVisitor {
    void UnitTest() {
        ShapeContainer theShapeContainer = new ShapeContainer();
        theShapeContainer.AddShape(new Sphere());
        theShapeContainer.AddShape(new Cube());
        theShapeContainer.AddShape(new Cylinder());

        theShapeContainer.RunVisitor(new DrawVisitor());
    }
}

文章整理自书籍《设计模式与游戏完美开发》 菜升达 著