Subclassing using lambdas

[lukaseder]

As originally reported by @C4Phone here: jOOQ/jOOL#331

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Hi, I just found out this library and jOOR. I really like your projects. I'd like it better if you guys could achieve "subclassing" interfaces and/or abstract classes using lambdas. This would be very helpful for using Java as an interpreted language.

Expected behavior and actual behavior:

I don't know whether similar functionalities exist. But this is what I expect:

// Run this code in a jupyter notebook.
interface Counter {
  // This is an interface, but it can also be an abstract class
  void add();
  void show();
}

org.joor.Reflect myClass = lambdaSubclass(on(Counter))
  .addField("counter", Integer.class)
  .setDefaultConstructor(self -> self.set("counter", 0))
  .set("add",  self -> self.set("counter", self.get("counter") +1)),
       "show", self -> System.out.println(self.get("counter")))  // "set" is a function of variable length.
  .doneSubclass();

Counter x = myClass.create();
x.add();
x.show();
x.add();
x.show();

// Should print 1 then print 2.

Is this possible or already implemented? If not, can I request this functionality and/or help implement it? Thank you!

[lukaseder]

Thanks for your suggestion. Essentially, you'd like to enhance the existing proxy implementation (which simply delegates getter and setter calls to a HashMap) with the possibility of specifying constructor and method implementations on that proxy?

[markzyu]

Yes. But I also worry that using these reflections too much is a bad practice and a reason to use Jython or Scala instead. So maybe people won't use this feature even if we implement it.