On Friday, 13 July 2012 at 19:35:34 UTC, Gor Gyolchanyan wrote:

The seed can't be an interface because it needs to contain state. For instance the progress towards becoming the respective fruit.

 The interface itself may not have state, but what uses the interface can have state. So i don't see an issue. Worse case you can use an abstract class which is a partial definition.

interface Counter {
  void addOne();
  int getCount();
}

//A contains state and is both A and Counter.
class A : Counter {
  int x;
  void addOne() {x++;}
  void getCount() {return x;}

}

The seed needs to be aware of the fruit it came from to access the fruit's DNA to inherit the traits of that fruit when it grows into a fruit of its own. (Please note, that it's just an example).

A fruit can have multiple such seeds, each of which must have it's own state and connection to the same fruit they came from.

so far...

class Fruit {
 class Seed {
  class Apple {}
 }
}

So, we start off by inheriting from Fruit, defining the properties of that fruit (It's an Apple, it's delicious and it goes great in a pie). Then we define several different types of Apple seeds, each of which need access to the apple.

Hmmm...
interface Seed {}

class Fruit {
  class Appleseed : Seed {
    class Apple {}
  }

  //or?
  static class Apple {
    class AppleSeed : Seed {} //multiple seeds, but need Fruit access?
  }
}

or perhaps...?

interface Seed{}
interface Fruit{}

//Apple knows it's a fruit..
class Apple : Fruit {
  //Appleseed is from the Apple (which is a fruit as well)
  //Appleseed is a seed, we can have multiple seeds from Apple, all which know
  //all about Apple's (and basic fruits) but not about non-appple seeds.
  class Appleseed : Seed {
  }
}