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auto-binding-dart is not working, fails with Bad State Error

问题描述:

I am trying to run this basic example of auto-binding-dart auto binding dart source. But it fails with

Breaking on exception: Bad state: Template must be cleared before a

new bindingDelegate can be assigned

I am doing this using stagehand polymerapp template.

index.html

<html>

<head>

<link rel="import" href="../lib/main_app.html">

<link rel="stylesheet" href="styles.css">

<script type="application/dart">export 'package:polymer/init.dart';</script>

</head>

<body unresolved>

<main-app></main-app>

</body>

</html>

main_app.html

<link rel="import" href="../../packages/polymer/polymer.html">

<polymer-element name="main-app">

<template id="my-template" is="auto-binding-dart">

<style>

:host {

display: block;

}

</style>

<div>Say something: <input value="{{value}}"></div>

<div>You said: {{value}}</div>

<button on-tap="{{buttonTap}}">Tap me!</button>

</template>

<script type="application/dart" src="main_app.dart"></script>

</polymer-element>

main_app.dart

import 'dart:html';

import 'package:polymer/polymer.dart';

@CustomTag('main-app')

class MainApp extends PolymerElement {

/// Constructor used to create instance of MainApp.

MainApp.created() : super.created();

ready(){

super.ready();

var template = document.querySelector('#my-template');

template.model = new MyModel();

}

}

class MyModel {

String value = 'something';

buttonTap() => window.console.info('tap!');

}

网友答案:

You don't need to use the <template is="auto-binding-dart"> inside another template.

The point of auto-binding-dart is to have a context for mustache binding outside a Polymer element. You could use auto-binding-dart instead of your main-app not inside.

I prefer an app-element (or main-app like you named) over auto-binding-dart because you don't need a main method this way.

The outermost <template> tag inside your <polymer-element ...> uses the elements class automatically as model (binding context).

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