从Base继承的基类属性

Question

I am doing a code review and have stumbled upon a situation where an abstract class is inheriting from an abstract base class that has a property of the inheriting class.

At the moment I am unable to debug the code to see how it would work, but I am assured that this has worked in production for many years.

As such it is a mystery to me how the following logic would work, step by step.

Inheritor:

public class Inheritor : Base {
  ...
  properties
  ...
}

Base:

public class Base {
  public Inheritor { get; set; }
  ...
  other properties
  ...
}

How is this possible?

Answer 1

An example in which it will hopefully make sense at a conceptual level:

public class Boss : Employee {
  ...
  properties
  ...
}

public class Employee {
  public Boss { get; set; }
  ...
  other properties
  ...
}

There might be many kinds of employees, but every one might have a boss (who is a particular kind of employee). Recall that properties of non-primitive types are references , so it's not the case that an Employee contains a Boss which (because it is also an Employee ) contains a Boss and so on. An Employee may refer to a Boss , which may refer to a Boss and so on. At some point, it stops at a Boss who doesn't have a Boss (the reference is null ), or it goes in circle.

Answer 2

I think you may be tripping over the relational concept of is-a versus has-a , where you are thinking that has-a somehow is constrained in the same way as is-a. An Inheritor is a Base and it would be very strange if the reciprocal were true: if a Base is also an Inheritor . But no reason why it cannot be that Base has an Inheritor .