如何使用其他集合的子数组数据过滤 mongo 集合子数组中的数据

Question

Baiscally制作节点.js，mongodb添加朋友功能，可以选择列表用户添加到朋友列表中，发送朋友请求，接受朋友请求，删除朋友请求，阻止朋友请求。

注册收集

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

let Register = new Schema(
First_Name:{
type: String,
required: true   
},
Last_Name: {
type: String
},
Email: {
type: String,
unique: true,
lowercase: true,
required: true
},
Friends:[{type: String}],  
});
module.exports = mongoose.model('Register', Register);

朋友收藏

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
var ObjectId = require('mongodb').ObjectID;
let Friends = new Schema({
Requester: {
type: ObjectId,
required: true
},
Recipients: [{Recipient:{type:ObjectId},Status:{type:Number}}],

}); 
module.exports = mongoose.model('Friends', Friends);

在节点内部.js发布 API

var Register = require('../models/register.model');
var Friends =require('../models/friends.model');
router.post('/getdata',function(req,res)
{
let Email="[e-mail]";
Register.findOne({ Email : Emails }, function(err, user) {
Friends.findOne({ Requester :user._id  }, function(err, user1) {
Register.find({$and:[{Friends:{$nin:[user._id]}},{_id:{$ne:user1.Recipients.Recipient}}]},function(err, user2) {
console.log("user2",user2);
//Here User2 data is not coming
//How to get data so can able to list user that is not added yet in FriendList
//Mainly user1.Recipients.Recipient this is not working because //Recipients is array so how can match all data with array, if i am //using loop then find return data scope ends on inside find closing //braces only.

//Any suggestion
});
});
});

Answer 1

因此，如果我正确的话，您需要执行以下操作：

1. 根据给定的电子邮件查找注册
2. 查找与此用户相关的好友
3. 查找尚未在用户好友列表中的注册

另外，鉴于您键入的内容，我假设 A 可以是 B 的朋友，但这并不意味着 B 是 A 的朋友。

虽然您当前拥有的数据结构可能不是最佳的，但我会向您展示正确的查询：

var Register = require('../models/register.model');
var Friends =require('../models/friends.model');
router.post('/getdata',function(req,res) {
const email = "[e-mail]";
Register.findOne({ Email: email }, function(err, user) { 
if (err) {
console.error(err);
return;
}
Friends.findOne({ Requester: user._id }, function(err, friend) {
if (err) {
console.error(err);
return;
}
const reciptientIds = friend.Recipients.map(function (recipient) {
return recipient.Recipient.toString();
});
Register.find({Friends: { $ne: user._id }, {_id: { $nin: recipientIds }}, function(err, notFriendedUsers) {
if (err) {
console.error(err);
return;
}
console.log(notFriendedUsers);
});
});
});
});

附言这个"回调地狱"可以使用承诺或等待/推迟轻松减少

Answer 2

终于能够解决它了，下面是解决方案

var Register = require('../models/register.model');
var Friends =require('../models/friends.model');
router.post('/getdata',function(req,res)
{
let Emails="[e-mail]";
Register.findOne({$and:[{ Email : Emails}] }, function(err, user) { 
if (err) {
console.error(err);
return;
}
Friends
.findOne({ Requester: user._id }, 
{ _id: 0} )
.sort({ Recipients: 1 })
.select( 'Recipients' )
.exec(function(err, docs){
docs = docs.Recipients.map(function(doc) { 
return doc.Recipient; });
if(err){
res.json(err)
} else {
console.log(docs,"docs");
Register.find({$and:[{Friends: { $ne: user._id }},{_id: { $nin: docs }},{_id:{$ne:user._id}}]}, function(err, notFriendedUsers) {
if (err) {
console.error(err);
return;
}
console.log(notFriendedUsers);
});
}
})
});