聚合物中的两个聚合物的火基收集元素如何嵌入到dom-repeat？ [英] How do you nest two of Polymer's firebase-collection elements inside dom-repeat?

问题描述

我有一个循环两个聚合物firebase集合元素的问题。
使用我的数据库结构，我首先必须检查用户可以访问哪些事件，然后从事件中获取该事件的信息。

此问题代码是，当我循环第二个firebase-collection时，事件上的数据绑定将一律重复，因此它将在每个h4上都是相同的名称。

$ b $那么在data ={{}}中有一个唯一变量的方法。
还是有更好的写出数据的方法？

 < firebase-collection data ={ userData}}location ={{_ getCorrectUrl（）}}>< / firebase-collection> 
< template is =dom-repeatitems ={{userData}}as =user> 
< firebase-collection data ={{events}}location ={{_ getCorrectEventsUrl（user .__ firebaseKey__）}}>< / firebase-collection> 
< template is =dom-repeatitems ={{events}}as =event> 
< h4> {{event.value.name}}< / h4> 
< / template> 
< / template> 
  

解决方案

我有一个解决方案，我认为不是最好的方法解决这个问题，但它对我有用。我创建了另一个名为我的用户的元素，我暴露了一个名为user的属性，该属性从第一个dom-repeat分配给用户的值。一切都行之有效，但我对此解决方案不满意。我仍然在寻找一个不涉及创建专用元素的解决方案。

 < firebase-collection data = {{userData}}location ={{_ getCorrectUrl（）}}> 
< / firebase-collection> 
< template is =dom-repeatitems ={{userData}}as =user> 
< my-user user =[[user]]>< / my-user> 
< / template> 
  

另一个我的用户：

 < dom-module id =my-user> 
< template> 
< firebase-collection data ={{events}}location ={{_ getCorrectEventsUrl（user）}}>< / firebase-collection> 
< template is =dom-repeatitems ={{events}}as =event> 
< h4> {{event.value.name}}< / h4> 
< / template> 
< / template> 
< script> 
（function（）{
 Polymer（{
 is：'my-user'，
 _getCorrectEventsUrl：function（obj）{
 return'https：// app .firebaseio.com / users /'+ obj .__ firebaseKey__; 
}，
属性：{
用户：{
类型：对象，
}，
}，
 
}）; 
}）（）; 
< / script> 
< / dom-module> 
  

编辑

现在在回答这个问题的某个时候，我意识到当有人面对NoSQL数据库的这种情况时，它通常会突出显示设计中的一个问题。数据应该被去规范化，并且应该避免加入，就像SQL数据库中通常所做的那样。观看 SQL开发人员的Firebase数据库在YouTube上

I have a problem of looping two of Polymers firebase-collection elements. With my database structure i first have to check which events the user has access to, then get the information on that event from events.

The problem with this code is that when i loop the second firebase-collection the data-binding on "events" will be the same on all that repeats and therefore it will be the same name on every h4.

So is there a way of having a unique variable in data="{{ }}". or is there a better way of writing out the data?

<firebase-collection data="{{userData}}" location="{{_getCorrectUrl()}}"></firebase-collection> 
<template is="dom-repeat" items="{{userData}}" as="user">
  <firebase-collection data="{{events}}" location="{{_getCorrectEventsUrl(user.__firebaseKey__)}}" ></firebase-collection> 
  <template is="dom-repeat" items="{{events}}" as="event">
    <h4>{{event.value.name}}</h4>
  </template>
</template>

解决方案

I have a solution which I consider not the best way to solve this issue, but it works for me. I created another element called 'my-user, I exposed an attribute called user which is assigned the value of user from the first dom-repeat. Everything works, however, I am not satisfied with this solution. I am still looking for a solution which doesn't involve creating a dedicated element for that.

<firebase-collection data="{{userData}}" location="{{_getCorrectUrl()}}">
</firebase-collection> 
<template is="dom-repeat" items="{{userData}}" as="user">
  <my-user user="[[user]]"></my-user>
</template>

and the other 'my-user':

<dom-module id="my-user">
<template>
  <firebase-collection data="{{events}}" location="{{_getCorrectEventsUrl(user)}}" ></firebase-collection> 
  <template is="dom-repeat" items="{{events}}" as="event">
    <h4>{{event.value.name}}</h4>
  </template>
</template>
<script>
    (function () {
  Polymer({
    is: 'my-user',
    _getCorrectEventsUrl: function(obj) {
      return 'https://app.firebaseio.com/users/' + obj.__firebaseKey__;
    },
    properties: {
      user:{
        type:Object,
      },
    },

  });
})();
</script>
</dom-module>

EDIT

Now after sometime of answering this question I came to realize that when someone face such a situation with NoSQL database, it usually highlights a problem in the design. Data should be de-normalized and one should avoid joining like what is normally done in SQL databases. Watch the The Firebase Database For SQL Developers on youtube.

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