Auto convert html string to element - dart

Question

Say I have a polymer-element <polymer-element> <div id="foo"> {{html}} </div> </polymer-element>, where html is supposed to be a HTML formated string, like <p>blah</p>, what I want is, when html changes, the polymer-element also changes, and use html as its innerHtml, i.e. auto convert the string to an element and insert it as foo's child.
Can polymer/polymer_expression do this for me, or I have to do a querySelector(), then set html as innerHtml manually?

Answer 1

My solution is a custom element that extends a div and uses the DocumentFragment class to parse HTML strings into the DOM via data binding.
From my Github gist
<!-- Polymer Dart element that allows HTML to be inserted into the DOM via data binding -->
<link rel="import" href="packages/polymer/polymer.html">
<polymer-element name="html-display" extends="div">
<script type="application/dart">
import 'dart:html';
import 'package:polymer/polymer.dart';
#CustomTag('html-display')
class HtmlDisplay extends DivElement with Polymer, Observable {
#published String htmlContent;
// we need this stuff because we're extending <div> instead of PolymerElement
factory HtmlDisplay() => new Element.tag('div', 'html-display');
HtmlDisplay.created() : super.created() {
polymerCreated();
}
#override void attached() {
super.attached();
}
// respond to any change in the "htmlContent" attribute
void htmlContentChanged(oldValue) {
if (htmlContent == null) {
htmlContent = "";
}
// creating a DocumentFragment allows for HTML parsing
this.nodes..clear()..add(new DocumentFragment.html("$htmlContent"));
}
}
</script>
</polymer-element>
<!--
Once you've imported the Polymer element's HTML file, you can use it from another Polymer element like so:
<link rel="import" href="html_display.html">
<div is="html-display" htmlContent="{{htmlString}}"></div>
*htmlString* can be something like "I <em>love</em> Polymer Dart!"
-->

Answer 2

I use solution as described in https://stackoverflow.com/a/20869025/789338.
The key class is DocumentFragment.

Answer 3

The official way to do it is described in the doc: https://www.polymer-project.org/docs/polymer/databinding-advanced.html#boundhtml
The example on the doc:
<polymer-element name="my-element">
<template>
<div id="message_area"></div>
</template>
<script>
Polymer({
message: 'hi there',
ready: function() {
this.injectBoundHTML('<b>{{message}}</b>', this.$.message_area);
}
});
</script>
</polymer-element>