猫鼬人口不能使这个工作？

Question

book.schema.js

const mongoose = require('mongoose')
const Schema = mongoose.Schema

const BookSchema = new Schema({
  name: {
    type: String,
    required: true
  }
})

module.exports = BookSchema

book.model.js

const mongoose = require('mongoose')
const BookSchema = require('../schema/book.schema')
const Book = mongoose.model('Book', BookSchema)

module.exports = Book

novel.schema.js

const mongoose = require('mongoose')
const Schema = mongoose.Schema

const NovelSchema = new Schema({
  name: {
     type: String,
     required: true
  },
  type: {
    type: Schema.Types.ObjectId,
    ref: 'Book'
  }
})

module.exports = NovelSchema

novel.model.js

const mongoose = require('mongoose')
const NovelSchema = require('../schema/novel.schema')
const Novel = mongoose.model('Novel', NovelSchema)

module.exports = Novel

查询

// Mongoose Populate cant get this to work
// I am at a loss
Novel.findById('5b87310d41073743856a7c4a').populate({
  path: 'books'
})

猫鼬无法正常工作。

请让我知道我在做错什么，或者给我一个简单的解释...谢谢...

Answer 1

函数populate（）上的参数是您要填充的字段的路径，并且当您在猫鼬中使用填充或任何链接函数时，您必须在末尾使用exec（）函数，因此正确这样做的方式是：

Novel.findById('5b87310d41073743856a7c4a').populate({
  path: 'type'
}).exec()

Answer 2

您可以使用填充来加载子文档，但是您需要在新颖模式中传递book字段的名称，在这种情况下，名称为 type 。

以下是一些示例的文档链接：Mongoose Populate

下面是解决问题的另一种方法：

let book = await new BookModel({name:"book test"}).save();
console.log('-----------BOOK ITEM-------------');
console.log(book);

let novel = await new NovelModel({name:"novel test",type:book._id}).save();
console.log('-----------NOVEL ITEM-------------');
console.log(novel);

let itemPopulated = await NovelModel.findById(novel._id)
    .populate('type')
    .then((result) => {
        return result;
    }).catch((err) => {
        console.log(err);
});
console.log('-----------ITEM POPULATED-------------');
console.log(itemPopulated);

执行输出：