修正责任链

Question

我非常了解责任链模式的基本知识。但是，我想问一下，是否可以动态地设置序列中的下一个接收器。

基本思想是，根据批准者的顺序，它将实例化下一个对象。

下面是一个例子：

抽象基类

public abstract class ApproverCategorizer
{
    protected ApproverCategorizer NextApprover { get; private set; }

    public ApproverCategorizer RegisterNextApprover(ApproverCategorizer nextApprover)
    {
        NextApprover = nextApprover;
        return nextApprover;
    }

    public abstract void ApproveAmount(TestEntity entity);

    protected bool IsLast(Queue<string> approverQueue)
    {
        return string.IsNullOrEmpty(approverQueue.Peek());
    }
}

高级审批人级

public class OfficerAApprover : ApproverCategorizer
{
    public override void ApproveAmount(TestEntity entity)
    {
        entity.ApproverQueue.Dequeue();

        if (entity.Amount <= 300)
        {
            entity.Status = "Approved";
            return;
        }

        if (!IsLast(entity.ApproverQueue) && string.IsNullOrWhiteSpace(entity.Status))
        {
            NextApprover.ApproveAmount(entity);
            return;
        }
        else
        {
            entity.Status = "Rejected";
        }

    }

}

军官B级

public class OfficerBApprover : ApproverCategorizer
{
    public override void ApproveAmount(TestEntity entity)
    {
        entity.ApproverQueue.Dequeue();

        if (entity.Amount <= 300)
        {
            entity.Status = "Approved";
            return;
        }

        if (!IsLast(entity.ApproverQueue) && string.IsNullOrWhiteSpace(entity.Status))
        {
            NextApprover.ApproveAmount(entity);
            return;
        }
        else
        {
            entity.Status = "Rejected";
        }

    }

}

认可链类

public class ApproverChain
{
    public static TestEntity Entity { get; set; }
    public static ApproverCategorizer Approver { get; set; }

    public ApproverChain()
    {
        List<string> approverList = Entity.ApproverList.Split(',').ToList();
        Queue<string> approverQueue = new Queue<string>();

        Approver = new StartApprover();
        // Note: The code below is working, but not the desired logic.
        //Approver.RegisterNextApprover(new OfficerAApprover()).RegisterNextApprover(new OfficerBApprover());

        // Note: This code below is not working, but this is the desired logic.
        foreach (string approver in approverList)
        {
            switch (approver)
            {
                case "OfficerA":
                    Approver.RegisterNextApprover(new OfficerAApprover());
                    break;
                case "OfficerB":
                    Approver.RegisterNextApprover(new OfficerBApprover());
                    break;
            }
            approverQueue.Enqueue(approver);

        }

        Entity.ApproverQueue = approverQueue;

    }

    public string StartProcess()
    {
        Approver.ApproveAmount(Entity);
        return Entity.Status;
    }
}

商务类

public string ProcessApproval()
{
  TestEntity entity = new TestEntity
  {
     Amount = 500,
     ApproverList = "OfficerB,OfficerA"
  };

  ApproverChain.Entity = entity;
  ApproverChain chain = new ApproverChain();
  var result = chain.StartProcess();

  return result;
}

这意味着OfficerB类将首先处理。如果失败，它将转到OfficerA类。

是否有一种方法可以将其调整为所需的逻辑？如果是的话，是如何做到的？

Answer 1

如果我正确理解，您需要通过运行时值(在本例中为string)配置您的审批者。

如果您的代码很少更改，这是可能的。这是所需的修改。

public ApproverChain()
{
    List<string> approverList = Entity.ApproverList.Split(',').ToList();
    Queue<string> approverQueue = new Queue<string>();

    Approver = new StartApprover();

    ApproverCategorizer currentApprover = Approver;
    foreach (string approver in approverList)
    {
        switch (approver)
        {
            case "OfficerA":
                currentApprover = currentApprover.RegisterNextApprover(new OfficerAApprover());
                break;
            case "OfficerB":
                currentApprover = currentApprover.RegisterNextApprover(new OfficerBApprover());
                break;
        }
        approverQueue.Enqueue(approver);
    }

    Entity.ApproverQueue = approverQueue;
}

上面的代码会运行得很好。但对我来说，ApproverQueue看起来很可疑。

似乎您使用ApproverQueue属性只是为了了解当前审批者是否是链中的最后一个审批者。您可以通过简单地将NextApprover检查为null并完全消除该approverQueue来找到它。

那么您的代码就变成了

public class ApproverChain
{
    public static TestEntity Entity { get; set; }
    public static ApproverCategorizer Approver { get; set; }

    public ApproverChain()
    {
        Approver = new StartApprover();

        List<string> approverList = Entity.ApproverList.Split(',').ToList();

        ApproverCategorizer currentApprover = Approver;
        foreach (string approver in approverList)
        {
            switch (approver)
            {
                case "OfficerA":
                    currentApprover = currentApprover.RegisterNextApprover(new OfficerAApprover());
                    break;
                case "OfficerB":
                    currentApprover = currentApprover.RegisterNextApprover(new OfficerBApprover());
                    break;
            }
        }
    }

    public string StartProcess()
    {
        Approver.ApproveAmount(Entity);
        return Entity.Status;
    }
}

public abstract class ApproverCategorizer
{
    protected ApproverCategorizer NextApprover { get; private set; }

    public ApproverCategorizer RegisterNextApprover(ApproverCategorizer nextApprover)
    {
        NextApprover = nextApprover;
        return nextApprover;
    }

    public abstract void ApproveAmount(TestEntity entity);

    protected bool IsLast()
    {
        return NextApprover == null;
    }
}

public class OfficerAApprover : ApproverCategorizer
{
    public override void ApproveAmount(TestEntity entity)
    {
        if (entity.Amount <= 300)
        {
            entity.Status = "Approved";
            return;
        }

        if (!IsLast() && string.IsNullOrWhiteSpace(entity.Status))
        {
            NextApprover.ApproveAmount(entity);
            return;
        }
        else
        {
            entity.Status = "Rejected";
        }
    }
}

而且您的TestEntity类将不具有ApproverQueue属性。