在聚合物1.2.3中，dom-repeat是否可以将内容用作模板并将值绑定到提供的元素？
自定义元素：
<dom-module id="modify-collection">
<template>
<div>
<template is="dom-repeat" items="[[collection]]">
<content></content>
</template>
</div>
</template>
</dom-module>
用法：
<modify-collection collection="{{things}}">
<list-item resource="[[item]]"></list-item>
</modify-collection>
我在没有帮助的情况下查看了以下资源：
Polymer: How to watch for change in <content> properties
Polymer 1.0 template bind ref equivalent
Data-binding between nested polymer elements
https://github.com/grappendorf/grapp-template-ref
https://github.com/Trakkasure/dom-bindref
https://github.com/Polymer/polymer/issues/1852
https://github.com/Polymer/polymer/pull/2196
<小时/> 更新2016-02-03 ：来自Polymer Team (PR #2196)，计划在未来为此提供更好的支持，以帮助解决一些缺点。
答案 0 :(得分：18)
解决方案2虽然更加冗长，但似乎效果最好。它还允许您动态选择模板，可能基于模型的属性。 （参见解决方案2：高级示例）
在这个简单的例子中发生了很多事情，包括模板化，“获取”阴影，阴影和光线之间的内容，当然还有数据绑定。
这个问题提供了一些见解，但没有Polymer 0.5's injectBoundHtml它就不可行（Using template defined in light dom inside a Polymer element）。当我们尝试使用innerHTML将元素复制到我们的模板时，我们的数据绑定似乎会丢失（AFAIK）。
因此，如果没有这个，我们就无法使用数据绑定动态创建模板。因此，两个解决方案都提前将内容包装在模板中;这导致html变为惰性，并允许Polymer在适当的时间（http://www.html5rocks.com/en/tutorials/webcomponents/template/）进行数据绑定。
如果您真的想了解所有内容，我建议您阅读src，lib/template/dom-repeat.html，lib/template/templatizer.html（约1500行）的聚合物lib/annotations/annotations.html。
有关改进的解决方案1，请参阅btelle's answer below。
请注意，此方法会导致dom-repeat无法自动呈现内容，因此我们会手动调用呈现。
<dom-module id="modify-collection">
<template>
<div>
<content></content>
<template id="repeater" is="dom-repeat" items="[[collection]]"></template>
</div>
</template>
<script>
...
ready: function() {
this.$.repeater.templatize(this.querySelector('#templ'));
}
_changeCollection: function(item) {
this.push('collection', item);
this.$.repeater.render();
}
</script>
</dom-module>
<modify-collection collection="{{things}}">
<template id="templ"><list-item resource="[[item]]"></list-item></template>
</modify-collection>
请注意，使用此内容因元素1而异，因为<template>必须具有is="dom-template"属性。
（稍微修改过这个PR：https://github.com/Polymer/polymer/pull/2196，最初基于https://github.com/grappendorf/grapp-template-ref）
!--
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-->
<!--
Portions of this code have been adapted from the `grapp-template-ref` element.
The original copyright notices are below.
-->
<!--
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Copyright (c) 2014-2015 Dirk Grappendorf, www.grappendorf.net
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-->
<!--
The `dom-ref` element is a custom `HTMLTemplateElement` type extension that
can be used to reference another template by id using the `ref` property.
`dom-bindref` accepts a `bind` property to bind an object to the referenced
template. By default the bound object can be accessed as `item`, this can be
changed using the `as` property.
Example:
```html
<template is="dom-template" id="template-bind"><span>[[item.key]]</span></template>
<template is="dom-ref" ref="template-bind" bind='{"key":"value"}'></dom-ref>
```
-->
<!-- <link rel="import" href="templatizer.html"> -->
<script>
Polymer({
is: 'dom-ref',
extends: 'template',
/**
* Fired whenever DOM is added or removed by this template (by
* default, rendering occurs lazily). To force immediate rendering, call
* `render`.
*
* @event dom-change
*/
properties: {
/**
* Reference to another template's id.
*/
ref: {
type: String,
observer: '_refChanged'
},
/**
* Object to be bound to referenced template.
*/
bind: {
type: Object,
observer: '_bindChanged'
},
/**
* The name of the variable to add to the binding scope for the
* element associated with a given template instance.
*/
as: {
type: String,
value: 'item'
}
},
behaviors: [
Polymer.Templatizer
],
ready: function() {
this.templatize(this);
},
attached: function() {
return this._stamp();
},
detached: function() {
return this._removeChildren();
},
_refChanged: function(newRef, oldRef) {
if (oldRef) {
this._removeChildren();
return this._stamp();
}
},
_bindChanged: function(newBind, oldBind) {
if (oldBind) {
this._removeChildren();
return this._stamp();
}
},
_stamp: function() {
var root, template, templateRoot, bind = {};
this._parent = Polymer.dom(this).parentNode;
root = this._parent;
while (Polymer.dom(root).parentNode) {
root = Polymer.dom(root).parentNode;
}
template = Polymer.dom(root).querySelector("template#" + this.ref);
// Check For Light Dom Elements that may be passed to this shadow root (Useful for: `<content></content>`)
if (!template) {
template = root.host.querySelector("template#" + this.ref);
}
// Check the whole document
if (!template) {
template = document.querySelector("template#" + this.ref);
}
bind[this.as] = this.bind;
// templateRoot = template.stamp(bind).root;
// Use this method until this lands: https://github.com/Polymer/polymer/pull/1889
templateRoot = (new template.ctor(bind, template)).root;
this._children = Array.prototype.slice.call(templateRoot.childNodes);
return Polymer.dom(this._parent).insertBefore(templateRoot, this);
},
_removeChildren: function() {
var child, i, len, ref, results;
if (this._children) {
ref = this._children;
results = [];
for (i = 0, len = ref.length; i < len; i++) {
child = ref[i];
results.push(Polymer.dom(this._parent).removeChild(child));
}
return results;
}
}
});
</script>
<dom-module id="modify-collection">
<template>
<div>
<content></content>
<template is="dom-repeat" items="[[collection]]">
<template is="dom-ref" bind="[[item]]" ref="templ"></template>
</template>
</div>
</template>
</dom-module>
<modify-collection collection="{{things}}">
<template id="templ" is="dom-template"><list-item resource="[[item]]"></list-item></template>
</modify-collection>
用法不会从上面改变。
我们在这里做的是介绍一个间接层，允许我们包装传递给我们元素的模板（在我们的例子中，带有叠加层）。
<dom-module id="modify-collection">
<template>
<div>
<content></content>
<template id="wrapper" is="dom-template">
<div class="overlay">
<template is="dom-ref" bind="[[item]]" ref="templ"></template>
</div>
</template>
<template is="dom-repeat" items="[[collection]]">
<template is="dom-ref" bind="[[item]]" ref="[[_templateRef(_overlayMode)]]"></template>
</template>
</div>
</template>
<script>
...
properties: {
_overlayMode: {
type: Boolean,
value: false
}
},
_templateRef: function(overlayMode) {
return overlayMode ? 'wrapper' : 'templ';
}
</script>
</dom-module>
答案 1 :(得分：6)
FWIW，看起来以下工作与解决方案1一样，并添加了通知路径（以及自动绑定/更改等）：
<dom-module id="i-me">
<template>
<content></content>
<template is="dom-repeat" id="repeater" items="[[collection]]"></template>
</template>
<script>
Polymer({
is: 'i-me',
properties: {
collection: {
type: Array,
value: [
{id: 1, name: 'a'},
{id: 2, name: 'b'}
],
notify: true
}
},
ready() {
this.$.repeater.templatize(this.querySelector('#templ'));
Polymer.Bind.prepareModel(this.$.repeater);
Polymer.Base.prepareModelNotifyPath(this.$.repeater);
}
});
</script>
</dom-module>
然后就这样使用：
<i-me>
<template id="templ">
<p><span>[[item.id]]</span>: <span>[[item.name]]</span></p>
</template>
</i-me>
答案 2 :(得分：2)
使用iron-list元素作为示例。这里抓取传递的模板元素https://github.com/PolymerElements/iron-list/blob/9909b73a00ecc91fb957232f7bc66b59435d66ad/iron-list.html#L830。
templatizer mixin用于AFAIK实现与传递模板的绑定（它也被<template is="dom-repeat">使用）