Node.js 嵌套MongoDB模式

我一直在从MongoDB网站上的在线主机学习MongoDB，我试图将产品链接到一个类别（例如，iPhone属于手机类别，它的祖先是电子产品），但是在嵌套时，我遇到了以下错误：

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

通过编写Schema.ObjectId和Schema.Types.ObjectId，我看到了几个问题，但在触发插入（保存）查询时，我将

错误转换为ObjectId

与此相关的问题还有几个：

如何确保在添加产品时，我也添加了其链接的类别

对于这种场景（添加子文档或引用模式），什么是最佳实践 PFB模型文件，为了执行CRUD操作，我在上面编写了控制器文件：

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;

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);

products.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;

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);

产品的输出结构示例：

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

---

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，在populate的帮助下，您可以通过

.populate（'parent'）

调用整个父模式

欲了解更多信息，请参阅：

---

谢谢。

但是当我添加mongoose.Schema.Types.ObjectId时，我尝试以以下方式插入数据：{“name”：“LG G4”，“pictures”：“price”：{“amount”：300，“currency”：“USD”}，“category”：“Laptops”}，我将错误转换为ObjectId。我将同时阅读关于populate的内容。这样做：-category:`{type:mongoose.Schema.Types.ObjectId，ref:'category'}`并且不要手动输入_id，因为mongodb将自动向数据库提供_id，该id在整个数据库中都是唯一的（随机ObjectId），但我仍然会收到消息：“值转换为ObjectId失败”错误。