gistfile1.txt

SomeGenericClass: class(ThePrototype) {
    .initialize: [a] {
        .a: a
    }

    .attribute("attr", get: { .a }, set: { .a: it })

    // Maybe this?
    .attribute("a", get: { .get_member("a") }, set: { .set_member("a", it) })
}

instance: SomeGenericClass(123)
instance.attr  //=> 123
instance.get_member("attr") //=> nil
instance.is_attribute("attr") //=> true