在聚合物和飞镖中渲染内容标签作为模板的一部分

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问题描述

我想使用聚合物和飞镖做一个通用列表。我扩展UL元素这样做。我想将模板变量放在此自定义元素的内容中。

I wish to make a generic list using polymer and dart. I am extending the UL element to do so. I want to place template variables within the content of this custom element.

<ul is="data-ul">
  <li>{{item['first_name']}}</li>
</ul>

自定义元素

<polymer-element name="data-ul" extends="ul">
  <template repeat="{{item in items}}">
      <content></content>
  </template>
  <script type="application/dart" src="data-ul.dart"></script>
</polymer-element>

我期待模板变量被插值，但它只是输出到DOM。

I was expecting the template variable to be interpolated however it simply gets outputted to the DOM as is. How do I output the content tag to be rendered as a template and not just directly outputted?

推荐答案

不幸的是，有两个问题这里。

Unfortunately, there are two issues here.

< content> 它是一个占位符，用于在Shadow DOM中的特定位置渲染轻DOM节点。第一个< content> 选择节点，获胜[]。

<content> cannot be used like this. It's a placeholder for rendering light DOM nodes at specific locations in the Shadow DOM. The first <content> that selects nodes, wins [1]. Stamping out a bunch like you're doing, while very intuitive, won't work as expected.

您正在混合聚合物的内部世界与外部世界外的元素。这真的意味着绑定（例如 {{}} ）仅在< polymer-element> 。

You're mixing the internal world of Polymer with the external world outside the element. What this really means is that bindings (e.g. {{}}) only work in the context of <polymer-element>.

你可以做的一件事是创建一个分布式的光DOM子文件的副本为 items 属性。在JavaScript中，这看起来像：

One thing you can do is create a copy of the distributed light DOM children as the items property of your element. In JavaScript this looks like:

<template repeat="{{item in items}}">
  <li>{{item['first_name']}}</li>
</template>
<content id="content" select="li"></content>
<script>
  Polymer('data-ul', {
    ready: function() {
      this.items = this.$.content.getDistributedNodes();
    }
  });
</script>

注意：我使用< content select =li> 是确保元素仅接受< li> 节点。如果你不担心用户使用其他类型的元素，只需使用 this.items = [] .slice.call（this.children）; 。

Note: The only reason I've used <content select="li"> is to insure the element only takes in <li> nodes. If you're not worried about users using other types of elements, just use this.items = [].slice.call(this.children);.

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