Enumerate properties of an object using meta class

gistfile1.groovy

class S {
  def propertiesAsMap() {
    this.metaClass.properties.collectEntries { p ->
      [(p.name): p.modifiers]
    }
  }
}

class A extends S {
  static int DEFAULT
  int x
}

def a = new A()
a.propertiesAsMap()  // -> [class:273, DEFAULT:9, x:1]

plus-settings.groovy

class S {
  S plus(S s) {
    def map = this.metaClass.properties.findAll { it.modifiers == 1 }.collectEntries {
      [(it.name): (s[it.name] != null) ? s[it.name] : this[it.name]]
    }
    this.metaClass.invokeConstructor(map)
  }
}

@groovy.transform.EqualsAndHashCode
@groovy.transform.ToString
class A extends S {
  static final A DEFAULT = new A(x: 100, y: 200)
  Integer x = null
  Integer y = null
}

def a1 = new A(x: 10)
def a2 = new A(y: 20)
a1 + a2