Is there a name for this construct with generics?

Question

I wrote this valid piece code, which made me wonder if there was a name for it:

public class GenericObject<T> {
    public T Obj { get; set; }
}
public class DerivedClass: GenericObject<DerivedClass> { }

This leads to the capability of:

var x = new DerivedClass();
x.Obj = x;
x.Obj.Obj = x;
x.Obj.Obj.Obj = x;
// ...
x.Obj.Obj.Obj.Obj.Obj.Obj.Obj.Obj.Obj.Obj...Obj = x;

Which is sure to raise a lot of eyebrows depending on the use case.

---

Is there a name for this? If so, what is it called, and what is a practical application?

Answer 1

Is there a name for this?

Ok, I may be misunderstanding your scenario, but I think what you're describing is generally called the "Curiously Recurring Template Pattern", CRTP for short.

It deserves mention and being named, but I don't think it is that odd, though; merely a common pattern that is not necessarily immediately obvious.

See:

• https://en.wikipedia.org/wiki/Curiously_recurring_template_pattern
• https://zpbappi.com/curiously-recurring-template-pattern-in-csharp

Generally, whenever you need the derived class information in the base class, you are probably looking for CRTP.

Bottom line: this pattern supports customization of the base class inheritance towards (for the purposes of) the derived class.

Answer 2

Not sure about the "official" name for such "pattern", but it can be used to "model" a hierarchy.

public class HierarchyItem<T>
{
    public T Parent { get; set; }
}

public class Person : HierarchyItem<Person>
{
    
}

Notice that this approach has a risk to create circular dependency.

To avoid possible circular dependencies design types based on the usage (do not try to describe "real life" with single object), instead has different types for different behaviours.

public class Relation<T>
{
    public T Parent { get; set; }
    public T Child { get; set; }
}