Groovy construct child from parent

childFromParent.groovy

class Parent {
  def fieldA
  
  Map asMap() {
    this.class.declaredFields.findAll { !it.synthetic }.collectEntries {
      ["${it.name}": this[it.name]]
    }
  }
}

class Child extends Parent {
  def fieldB
}

parent = new Parent(fieldA: "value")


child = parent.asMap() as Child


assert child.fieldA == parent.fieldA
assert child != parent
assert child instanceof Child

usginSubMap.groovy

class Parent {
  def fieldA
}

class Child extends Parent {
  def fieldB
}

def att = parent.properties - parent.properties.subMap('class', 'metaClass')
new Child(att)