问在聚合物飞镖中，从父母到孩子的沟通方式是什么？

EN

library my_element;

import 'package:polymer/polymer.dart';
import 'dart:html';
import 'dart:async';

@CustomTag('my-element')
class MyElement extends PolymerElement {
  MyElement.created() : super.created() {

    // NOTE this only fires once,
    // see https://groups.google.com/forum/#!topic/polymer-dev/llfRAC_cMIo
    // This is useful for waiting for a node to change in response
    // to some data change. Since we don't know when the node will
    // change, we can use onMutation.
    onMutation($['list']).then((List<MutationRecord> records) {
      $['out'].text = 'Change detected at ${new DateTime.now()}';
    });

    new Timer(const Duration(seconds:1), () {
      $['list'].children.add(new LIElement()..text='hello from timer');
    });
  }
}

  /**
   * Observes the target for the specified changes.
   *
   * Some requirements for the optional parameters:
   *
   * * Either childList, attributes or characterData must be true.
   * * If attributeOldValue is true then attributes must also be true.
   * * If attributeFilter is specified then attributes must be true.
   * * If characterDataOldValue is true then characterData must be true.
   */
  void observe(Node target,
               {bool childList,
                bool attributes,
                bool characterData,
                bool subtree,
                bool attributeOldValue,
                bool characterDataOldValue,
                List<String> attributeFilter}) {

library my_element;

import 'package:polymer/polymer.dart';
import 'dart:html';
import 'dart:async';

@CustomTag('my-element')
class MyElement extends PolymerElement {
  MyElement.created() : super.created() {
  }

  myCustomMethod(param){
    print("pass-in param = $param");
  }

}

  (theParentClass.querySelector("my-element") as MyElement).myCustomMethod({"done":true});