MongoDB - Mongoose：如何查询？ "populate()"剂量不起作用。这是表演"null"

Question

我有一个页面架构，该页面架构有两个对象属性createdBy和approvedBy。

当我使用.populate("approvedBy").populate("createdBy");然后显示"approvedBy": null , "createdBy": null，

当我不使用populate()时，只使用find()，然后显示ObjectId。但我需要所有的嵌套对象，比如使用populate().

页面架构：

const mongoose = require("mongoose");
const PageSchema = new mongoose.Schema({
title: {
type: String,
require: true,
},
description: {
type: String,
require: true,
},
url: {
type: String,
},
logoURL: {
type: String,
},
backgroundImageURL: {
type: String,
},
button: {
title: {
type: String,
require: true,
},
url: {
type: String,
},
color: {
type: String,
},
},
createdBy: {
type: mongoose.Types.ObjectId,
ref: "User",
require: true,
},
approvedBy: {
type: mongoose.Types.ObjectId,
ref: "User",
require: true,
},
approve: {
type: Boolean,
default: false,
},
approveDate: {
type: Date,
},
archive: {
type: Boolean,
default: false,
},
archiveDate: {
type: Date,
},
createdAt: {
type: Date,
default: Date.now,
},
updatedAt: {
type: Date,
},
});
module.exports = mongoose.model("Page", PageSchema);

使用find()代码：

const pages = async (req, res, next) => {
try {
const pages = await Page.find({})
.populate("approvedBy")
.populate("createdBy");
if (pages === null || pages.length == 0) {
throw createError(404, "NO DATA FOUND");
}
return res.status(200).json({ success: 1, pages });
} catch (error) {
return next(createError(error));
}
};

通过使用find()输出：

{
"success": 1,
"pages": [
{
"button": {
"title": "Play Now",
"url": "btnURL",
"color": "#ff6767"
},
"_id": "6425a0d069c436a4f056ba26",
"title": "Dengen NFT 2",
"description": "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.",
"url": "imgURL",
"logoURL": "logoURL",
"backgroundImageURL": "bgURL",
"createdBy": "64231bf9f21deb779a148c64",
"approve": false,
"archive": false,
"createdAt": "2023-03-30T14:46:40.312Z",
"__v": 0,
"approvedBy": "64231b8a6c0398e50a8472d1"
}
]
}

使用.populate("approvedBy").populate("createdBy")代码：

const pages = async (req, res, next) => {
try {
const pages = await Page.find({}).populate("approvedBy", "createdBy");
if (pages === null || pages.length == 0) {
throw createError(404, "NO DATA FOUND");
}
return res.status(200).json({ success: 1, pages });
} catch (error) {
return next(createError(error));
}
};

通过使用.populate("approvedBy").populate("createdBy")输出：

"approvedBy": null , "createdBy": null，

{
"success": 1,
"pages": [
{
"button": {
"title": "Play Now",
"url": "btnURL",
"color": "#ff6767"
},
"_id": "6425a0d069c436a4f056ba26",
"title": "Dengen NFT 2",
"description": "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.",
"url": "imgURL",
"logoURL": "logoURL",
"backgroundImageURL": "bgURL",
"createdBy": null,
"approve": false,
"archive": false,
"createdAt": "2023-03-30T14:46:40.312Z",
"__v": 0,
"approvedBy": null
}
]
}

Answer 1

你说你在使用：
.populate("approvedBy").populate("createdBy")
但你发布了这个：
.populate("approvedBy", "createdBy")，我不确定它是否有效。

这个代码是有效的，也许你可以从中吸取一些东西：

import mongoose from "mongoose"
const UserSchema = new mongoose.Schema({
name: String
})
const PageSchema = new mongoose.Schema({
createdBy: {
type: mongoose.Types.ObjectId,
ref: "User",
require: true,
},
approvedBy: {
type: mongoose.Types.ObjectId,
ref: "User",
require: true,
},
});
const Page = mongoose.model("Page", PageSchema);
const User = mongoose.model("User", UserSchema);
const run = async () => {
await mongoose.connect('mongodb://127.0.0.1:27017/75890536');
const { _id } = await User.create({ name: "username" })
await Page.create(
{
createdBy: _id,
approvedBy: _id
})
const page = await Page.find().populate("createdBy").populate("approvedBy")
console.log(page)
await mongoose.disconnect()
}
run()

输出：

[
{
_id: new ObjectId("6425c5a767056db481c1f77f"),
createdBy: {
_id: new ObjectId("6425c5a767056db481c1f77d"),
name: 'username',
__v: 0
},
approvedBy: {
_id: new ObjectId("6425c5a767056db481c1f77d"),
name: 'username',
__v: 0
},
__v: 0
}
]

节点：v18.12.1mongo v6.0.1