如何在Meteor中呈现嵌套集合？(How to render nested collections in Meteor?)

 概要： 
 嵌套在父类别中的子类别不会在流星模板中呈现。 
 
 细节： 
 考虑一下'Category'的数据模型： 
 
// Model Schema
Category {
   idCategory : 20, (id of the category itself)
   idCategoryParent : 0, (idCategory of our parent category)
   defaultLabel : "Movies" (our label)
}
 
 有父类别和子类别。 父类别的idCategoryParent属性值为0.子类别将其父类的idCategory作为它们的idCategoryParent属性进行存储。 我试图循环访问这些类别的一个集合，并按以下方式呈现它们： 
 
<b>Movies</b> // parent category is in bold
<ul> // child categories are rendered as an unordered list
  <li>Horror</li> 
  <li>Comedy</li>
  <li>Action</li>
  <li>Drama</li>
</ul>

<b>Music</b>
<ul>
  <li>Rock</li> 
  <li>Classical</li>
  <li>Ambient</li>
</ul>
 
 但是，这是我实际得到的： 
 
<b>Movies</b>
<ul> // empty...
</ul>

<b>Music</b>
<ul>
</ul>
 
 源代码： 
 
// How we get the 'categories_parents' data
Template.content.categories_parents = function (){ 

    /*
    * Get all parent categories (categories with an idCategoryParent of 0)
    */
    var parents = Categories.find({idCategoryParent:0});
    var pCount = parents.count();

    for (var i = 0; i < pCount; i++){

            var pId = parents.db_objects[i]['idCategory'];
            /* 
            * Get all child categories of the parent (categories with
            * an idCategoryParent equal to value of parent category's idCategory).
            */
            var children = Categories.find({idCategoryParent:pId});
            var cCount = children.count();

            /*
            * Assign the child categories array as a property of the parent category
            * so that we can access it easily in the template #each expression
            */
            parents.db_objects[i]['children'] = children;
    }

    return parents;
}


// This is our template
<template name="content">
<h1>Categories</h1>
    {{#each categories_parents}}
        <b>{{defaultLabel}}</b><br />
        <ul>
            {{#each children}}
            <li>{{defaultLabel}}</li>
            {{/each}}
        </ul>
    {{/each}}
</template>
 
 其他模板配置我曾尝试进行故障排除： 
 
{{#each children}}
<li>A Child Exists Here</li> // Even this never rendered... no children?
{{/each}}
 
 任何线索，为什么发生这种情况将不胜感激。 

Summary:
 Child categories nested inside of Parent Categories are not getting rendered in a Meteor template.
 
Details:
 Consider a data model for 'Category' as such:
 
// Model Schema
Category {
   idCategory : 20, (id of the category itself)
   idCategoryParent : 0, (idCategory of our parent category)
   defaultLabel : "Movies" (our label)
}
 
There are parent categories and child categories. Parent categories have an idCategoryParent property value of 0. Child categories store the idCategory of their parents as their idCategoryParent property. I'm trying to loop through a collection of these Categories and render them in the following way: 
 
<b>Movies</b> // parent category is in bold
<ul> // child categories are rendered as an unordered list
  <li>Horror</li> 
  <li>Comedy</li>
  <li>Action</li>
  <li>Drama</li>
</ul>

<b>Music</b>
<ul>
  <li>Rock</li> 
  <li>Classical</li>
  <li>Ambient</li>
</ul>
 
However, this is what I actually get:
 
<b>Movies</b>
<ul> // empty...
</ul>

<b>Music</b>
<ul>
</ul>
 
Source Code:
 
// How we get the 'categories_parents' data
Template.content.categories_parents = function (){ 

    /*
    * Get all parent categories (categories with an idCategoryParent of 0)
    */
    var parents = Categories.find({idCategoryParent:0});
    var pCount = parents.count();

    for (var i = 0; i < pCount; i++){

            var pId = parents.db_objects[i]['idCategory'];
            /* 
            * Get all child categories of the parent (categories with
            * an idCategoryParent equal to value of parent category's idCategory).
            */
            var children = Categories.find({idCategoryParent:pId});
            var cCount = children.count();

            /*
            * Assign the child categories array as a property of the parent category
            * so that we can access it easily in the template #each expression
            */
            parents.db_objects[i]['children'] = children;
    }

    return parents;
}


// This is our template
<template name="content">
<h1>Categories</h1>
    {{#each categories_parents}}
        <b>{{defaultLabel}}</b><br />
        <ul>
            {{#each children}}
            <li>{{defaultLabel}}</li>
            {{/each}}
        </ul>
    {{/each}}
</template>
 
Other template configurations I have tried in troubleshooting:
 
{{#each children}}
<li>A Child Exists Here</li> // Even this never rendered... no children?
{{/each}}
 
Any clues as to why this is happening would be appreciated. 

原文：https://stackoverflow.com/questions/13750854