如何使我的业务对象层在其方法中使用管理层？

Question

I have a solution in VS2010 with several projects, each making up a layer within my application. I have business entities which are currently objects with no methods, and I have a management layer which references the business entities layer in it's project. I now think I have designed my application poorly and would like to move methods from helper classes (which are in another layer) into methods I'll create within the business entities themselves.

For example I have a VirtualMachine object, which uses a helper class to call a Reboot() method on it which passes the request to the management layer. The static manager class talks to an API that reboots the VM. I want to move the Reboot() method into the VirtualMachine object, but I will need to reference the management layer:

public void Reboot()
{  
    VMManager.Reboot(this.Name);
}

So if I add a reference to my management project in my entities project, I get the circular dependency error, which is how it should be. How can I sort this situation out? Do I need to an yet another layer between the entity layer and the management layer? Or, should I just forget it and leave it as it is.

The application works ok now, but I am concerned my design isn't particularly OOP centric and I would like to correct this.

Answer 1

You are correct, you should not make circular references, making another layer might just help you avoid the circular reference error, but it will still be a circular reference, if i understood you correctly.

I would sit down, draw a map and methods should ONLY call down in layers. That is the most general methods at the "bottom" of the program, and the more specialized you get the higher up in the hierarchy you should put it.

The API of the program you are making should be on the bottom of this hierarchy.

You might not need to redesign your whole project. But it sounds like you could help yourself with visualizing the structure.

Answer 2

Management layer (as it is the one doing the work) does not seem to fit on the top of Business layer. And actually we do not have such a layer above Business layer, we only have facade layer at the top of Business layer - which is not the same as what you need.

From what I can see in your project, you need the business layer to use services of the helper class:

// Business layer
public class VirtualMachineManager
{
   IRebooter _rebooter;
   public class(IRebooter rebooter)
   {
      _rebooter = rebooter;
   }
}

// helper class
public class Rebooter : IRebooter 
{
   ....
}