linux檔案共享

阿新 • • 發佈：2021-11-22

編輯說明

概述

表示一個作用於某物件結構中的各元素的操作。它使你可以在不改變各元素的類的前提下定義作用於這些元素的新操作

允許一個或者多個操作應用到一組物件上，解耦操作和物件本身

但為了避免不斷新增功能導致類不斷膨脹，職責越來越不單一，以及避免頻繁地新增功能導致的頻繁程式碼修改，我們使用訪問者模式，將物件與操作解耦，將這些業務操作抽離出來，定義在獨立細分的訪問者類

結構圖

程式碼實現

元素

    /// <summary>
    /// 抽象元素
    /// </summary>
    public abstract class Element
    {
         
public abstract void Accept(Visitor visitor);
    }

    /// <summary>
    /// 具體元素A
    /// </summary>
    public class ConcreteElementA : Element
    {
        public override void Accept(Visitor visitor)
        {
            visitor.VisitConcreteElementA(this);
        }

        public void OperationA()
        { }
    }

    /// <summary>
    /// 具體元素B
    /// </summary>
    public class ConcreteElementB : Element
    {
        public override void Accept(Visitor visitor)
        {
            visitor.VisitConcreteElementB(this);
        }

        public void OperationB()
        { }
    }

訪問者

    /// <summary> 

    /// 抽象訪問者
    /// </summary>
    public abstract class Visitor
    {
        public abstract void VisitConcreteElementA(ConcreteElementA concreteElementA);

        public abstract void VisitConcreteElementB(ConcreteElementB concreteElementB);
    }

    /// <summary>
    /// 具體訪問者1
    /// </summary>
    public class ConcreteVisitor1 : Visitor
    {
        public override void VisitConcreteElementA(ConcreteElementA concreteElementA)
        {
            Console.WriteLine("{0}被{1}訪問", concreteElementA.GetType().Name, this.GetType().Name);
        }

        public override void VisitConcreteElementB(ConcreteElementB concreteElementB)
        {
            Console.WriteLine("{0}被{1}訪問", concreteElementB.GetType().Name, this.GetType().Name);
        }
    }

    /// <summary>
    /// 具體訪問者2
    /// </summary>
    public class ConcreteVisitor2 : Visitor
    {
        public override void VisitConcreteElementA(ConcreteElementA concreteElementA)
        {
            Console.WriteLine("{0}被{1}訪問", concreteElementA.GetType().Name, this.GetType().Name);
        }

        public override void VisitConcreteElementB(ConcreteElementB concreteElementB)
        {
            Console.WriteLine("{0}被{1}訪問", concreteElementB.GetType().Name, this.GetType().Name);
        }
    }

物件結構

    /// <summary>
    /// 物件結構
    /// </summary>
    public class ObjectStructure
    {
        private IList<Element> elements = new List<Element>();

        public void Attach(Element element)
        {
            elements.Add(element);
        }

        public void Detach(Element element)
        {
            elements.Remove(element);
        }

        public void Accept(Visitor visitor)
        {
            foreach (Element e in elements)
            {
                e.Accept(visitor);
            }
        }
    }

客戶端

    class Program
    {
        static void Main(string[] args)
        {
            ObjectStructure o = new ObjectStructure();
            o.Attach(new ConcreteElementA());
            o.Attach(new ConcreteElementB());

            ConcreteVisitor1 v1 = new ConcreteVisitor1();
            ConcreteVisitor2 v2 = new ConcreteVisitor2();

            o.Accept(v1);
            o.Accept(v2);

            Console.Read();
        }
    }