CODEWITHSUNDEEP
dartdart-polymer
davesdig
davesdig

Reputation: 63

When dynamically adding dart polymer elements, how do I get observable variables to on DOM

I am trying to change the default web application that uses the polymer library so that the polymer element is created and added to the DOM from DART code rather than including in the HTML. I have succeeded in adding the element to the DOM, but my observable variable are not being updated on the DOM. The events are being fired, and the values are changing. I have got the DOM to update using Observable.dirtyCheck(), however, this is apparently expensive, so am trying to figure out how to get polymer to update dom without dirtyCheck().

So, In short, how to I get rid of Observable.dirtyCheck()???

dynamiccreate.dart

library dynamiccreate;

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



main() {
  initPolymer();

  //create click-counter element at runtime from DART, not HTML
  var NewElement = new Element.tag('click-counter');
  NewElement.setAttribute("count", "5");
  //Add to DOM
  querySelector('#sample_container_id').children.add(NewElement);
}

dynamiccreate.html

<!DOCTYPE html>

<html>
  <head>
    <meta charset="utf-8">
    <title>Sample app</title>
    <link rel="stylesheet" href="dynamiccreate.css">

    <!-- import the click-counter -->
    <link rel="import" href="clickcounter.html">
    <!-- <script type="application/dart">export 'package:polymer/init.dart';</script> -->
    <script src="packages/browser/dart.js"></script>
  </head>
  <body>
    <h1>DynamicCreate</h1>

    <p>Hello world from Dart!</p>

    <div id="sample_container_id">
     <!--  <click-counter count="5"></click-counter> -->
    </div>
    <script src="dynamiccreate.dart" type="application/dart"></script>
  </body>
</html>

clickcounter.dart

import 'package:polymer/polymer.dart';

/**
 * A Polymer click counter element.
 */
@CustomTag('click-counter')
class ClickCounter extends PolymerElement {
  @published int count = 0;

  ClickCounter.created() : super.created() {
  }

  //increment gets called when dynamically adding object at runtime
  //But does not update count on DOM
  void increment() {
    count++;
    //Have to add this to update count in DOM
    Observable.dirtyCheck(); //<<<---How do I get rid of this???
  }
}

clickcounter.html

<polymer-element name="click-counter" attributes="count">
  <template>
    <style>
      div {
        font-size: 24pt;
        text-align: center;
        margin-top: 140px;
      }
      button {
        font-size: 24pt;
        margin-bottom: 20px;
      }
    </style>
    <div>
      <button on-click="{{increment}}">Click me</button><br>
      <span>(click count: {{count}})</span>
    </div>
  </template>
  <script type="application/dart" src="clickcounter.dart"></script>
</polymer-element>

Upvotes: 2

Views: 2801

Answers (1)

Shailen Tuli
Shailen Tuli

Reputation: 14161

Change your dynamiccreate.dart file to look like this, and the counter starts incrementing in the UI:

library dynamiccreate;

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

main() {
  initPolymer().run(() {
    var newElement = new Element.tag('click-counter');
    newElement.setAttribute("count", "15");
    querySelector('#sample_container_id').children.add(newElement);
  });
}

Nit: name your variable newElement, not NewElement. Fixed here.

Upvotes: 5

Related Questions