嵌套 MongoDB 模式

Question

我一直在从他们网站上托管的在线Webinar 中学习 MongoDB，我正在尝试将 Products 链接到一个类别（例如，iPhone 属于具有诸如 Electronics 之类的祖先的 Mobiles 类别），但是在嵌套时我'收到以下错误：

MongooseError: Schema hasn't been registered for model "Category".
Use mongoose.model(name, schema)

我通过编写 Schema.ObjectId 和 Schema.Types.ObjectId 看到了几个问题，但是在触发插入（保存）查询时我得到了Cast Error to ObjectId。

还有几个与这些相关的问题：

1. 如何确保在添加产品时，我还添加了它链接到的类别？
2. 对于这种情况（添加子文档或参考架构），最佳实践是什么？

PFB 模型文件，我在上面写了控制器文件以执行 CRUD 操作：

category.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var categorySchema = new Schema({
  _id: { type: String },
  parent: {
    type: String,
    ref: 'Category'
  },
  ancestors: [{
    type: String,
    ref: 'Category'
  }]
});

module.exports.categorySchema = categorySchema;

products.js

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var Category = require('./category');
var fx = require('./fx');

var productSchema = new mongoose.Schema({
  name: { type: String, required: true },
  // Pictures must start with "http://"
  pictures: [{ type: String, match: /^http:\/\//i }],
  price: {
    amount: {
      type: Number,
      required: true,
      set: function(v) {
        this.internal.approximatePriceUSD =
          v / (fx()[this.price.currency] || 1);
        return v;
      }
    },
    // Only 3 supported currencies for now
    currency: {
      type: String,
      enum: ['USD', 'EUR', 'GBP'],
      required: true,
      set: function(v) {
        this.internal.approximatePriceUSD =
          this.price.amount / (fx()[v] || 1);
        return v;
      }
    }
  },
  category: { type: Schema.ObjectId,ref: 'Category'},
  internal: {
    approximatePriceUSD: Number
  }
});

//var schema = new mongoose.Schema(productSchema);

var currencySymbols = {
  'USD': '$',
  'EUR': '€',
  'GBP': '£'
};

/*
 * Human-readable string form of price - "$25" rather
 * than "25 USD"
 */
productSchema.virtual('displayPrice').get(function() {
  return currencySymbols[this.price.currency] +
    '' + this.price.amount;
});

productSchema.set('toObject', { virtuals: true });
productSchema.set('toJSON', { virtuals: true });

module.exports = mongoose.model("Product", productSchema);

产品的示例输出结构：

{
    "_id": "**autogeneratedByMongo",
    "name":"iPhone",
    "category":{
        "_id":"Mobiles", 
        "ancestors":["Electronics","Mobiles"]
    }
    ....
}

Answer 1

将type 键的值更改为mongoose.Schema.Types.ObjectId，它将链接到您要引用的特定ObjectId，并且在填充的帮助下，您可以通过.populate('parent') 调用整个父架构。

有关我的更多信息，请参阅：- populate

谢谢。