Using modular traits in Groovy 2.3.0-beta-1

ModularGroovyTraits

trait HasId {
    long id
}
trait HasVersion {
    long version
}
trait Persistent {
    boolean save() { println "saving ${this.dump()}" }
}
trait Entity implements Persistent, HasId, HasVersion {
    boolean save() {
        version++
        Persistent.super.save()
    }
}

class Publication implements Entity {
    String title
}

class Book extends Publication {
    String isbn
}

Entity gina = new Book(id:1, version:1, title:"gina", isbn:"111111")
gina.save()
assert gina.version == 2