Looking for a general way to implement a function in a base class

Question

I am trying to perform a simple implementation of the Specification template at my domain level.

If I have a static class full of specifications like this:

public static class FooSpecifications
{
  public static Func<Foo, bool> IsSuperhuman
  {
    get
    {
      return foo => foo.CanShootLasersOutOfItsEyes && foo.CanFly;
    }
  }
}

Then I can do wonderful things like this:

IEnumerable<Foo> foos = GetAllMyFoos();
var superFoos = foos.Where(FooSpecifications.IsSuperhuman);

I can also add the bool method to Foo to determine if a particular instance meets the specification:

public bool Meets(Func<Foo, bool> specification)
{
  return specification.Invoke(this);
}

Given that Foo, like all my domain objects, extends DomainObject, is there a way I can put a generic implementation of Meets () in DomainObject to keep me in the Meets () implementation separately in each entity?

Answer 1

Something like that...

    public abstract class DomainObj<T> // T - derived type
        where T : DomainObj<T>
    {
        public bool Meets(Func<T, bool> specification)
        {
            return specification.Invoke((T) this);
        }
    }

    public class Foo : DomainObj<Foo> {}

    public class Bar : DomainObj<Bar> {}       

        Func<Foo, bool> foospec = x => true;
        Func<Bar, bool> barspec = x => true;

        var foo = new Foo();
        var bar = new Bar();
        foo.Meets(foospec);
        foo.Meets(barspec); // won't compile because of mismatched types of spec and object instance

EDIT

, Meet . .

    public abstract class DomainObj
    {
    }

    public static class DomainObjExtensions
    {
        public static bool Meets<T>(this T obj, Func<T, bool> f)
            where T : DomainObj
        {
            return f(obj);
        }
    }

    public class Foo : DomainObj {}

    public class Bar : DomainObj {}

    Func<Foo, bool> foospec = x => true;
    Func<Bar, bool> barspec = x => true;

    var foo = new Foo();
    var bar = new Bar();
    foo.Meets(foospec);
    foo.Meets(barspec); // error