社交网站回复功能故障：刷新后消失且用户信息不显示

当前遇到的问题 #

• 新增的回复已存入数据库，但页面刷新后就消失
• 回复无法显示用户名和头像
• 疑问：旧版嵌套回复的Post Schema是否支持回复的删除与编辑功能

相关代码 #

旧版Post Model #

import mongoose from "mongoose";

const postSchema = mongoose.Schema({
    postedBy: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User',
        required: true
    },
    text: {
        type: String,
        maxLength: 500
    },
    img: {
        type: String,
    },
    likes: [{
        // array of user id's
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
        default: []
    }],
    saves: [{
        // array of user id's
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
        default: []
    }],
    replies: [
        {
        userId: {
            type: mongoose.Schema.Types.ObjectId,
            ref: "User",
            required: true
        },
        text: {
            type: String,
            required: true
        },
        userProfilePic: {
            type: String
        },
        username: {
            type: String
        }
    }
    ]
}, {timestamps: true}
)

const Post = mongoose.model('Post', postSchema);

export default Post;

新版Post Model #

import mongoose from "mongoose";

const postSchema = mongoose.Schema({
    postedBy: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'User',
        required: true
    },
    text: {
        type: String,
        maxLength: 500
    },
    img: {
        type: String,
    },
    video: {
        type: String,
        ref: "Upload"
    },
    likes: [{
        // array of user id's
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
        default: []
    }],
    saves: [{
        // array of user id's
        type: mongoose.Schema.Types.ObjectId,
        ref: "User",
        default: []
    }],
    replies: [{
                type: mongoose.Schema.Types.ObjectId,
                ref: 'Replies',
                userId: {
                    type: mongoose.Schema.Types.ObjectId,
                    ref: "User",
                    required: true
                },
        }]
}, {timestamps: true}
)

const Post = mongoose.model('Post', postSchema);

export default Post;

Reply Model #

import mongoose from "mongoose";

const ReplySchema = mongoose.Schema({
    text: {
        type: String,
        required: true
    },
    tag: Object,
    reply: mongoose.Types.ObjectId,
    likes: [{ type: mongoose.Types.ObjectId, ref: 'User' }],
    user: { type: mongoose.Types.ObjectId, ref: "User" },
}, {
    timestamps: true
})

const Reply = mongoose.model('Replies', ReplySchema);

export default Reply;

Controller函数 #

const replyCtrl = {
    createReply: async(req, res) => {
        try {
            const { postId, text, tag, comment } = req.body;

            const newReply = new Reply({
                user: req.user._id, text, tag, comment
            })

            await Post.findOneAndUpdate({_id: postId}, {
                $push: {replies: newReply._id}
            }, {new: true})

            await newReply.save();

            res.status(200).json(newReply)
        } catch (err) {
            console.log(err)
        }
    }
}

问题解决 #

1. 回复刷新消失+不显示用户名/头像的原因及修复 #

核心问题：

• 新版Post模型的replies字段定义冗余：嵌套的userId完全多余，用户信息已存储在Reply模型中，正确定义应为单纯的ObjectId数组关联Replies
• 获取帖子数据时未执行关联查询（populate），无法拿到回复及对应的用户信息

修复步骤：

第一步：修正新版Post模型的replies字段

// 替换原有replies字段定义
replies: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Replies'
}]

第二步：修改createReply控制器，返回关联用户信息的回复

const replyCtrl = {
    createReply: async(req, res) => {
        try {
            const { postId, text, tag, comment } = req.body;

            const newReply = new Reply({
                user: req.user._id, text, tag, reply: comment // 参数名与Reply模型字段保持一致
            })

            // 先保存回复，再更新帖子关联关系
            await newReply.save();
            await Post.findOneAndUpdate({_id: postId}, {
                $push: {replies: newReply._id}
            }, {new: true})

            // 关联查询用户信息后返回，仅获取需要的字段
            const populatedReply = await Reply.findById(newReply._id).populate('user', 'username profilePic');
            res.status(200).json(populatedReply)
        } catch (err) {
            console.log(err)
            res.status(500).json({msg: '创建回复失败'})
        }
    }
}

第三步：获取帖子时关联回复及用户信息

在获取帖子的接口中，需要嵌套关联查询：

const posts = await Post.find()
    .populate('postedBy', 'username profilePic')
    .populate({
        path: 'replies',
        populate: {
            path: 'user',
            select: 'username profilePic' // 仅返回用户名和头像字段
        }
    })

2. 旧版嵌套Schema能否实现回复的删除与编辑？ #

完全可以，利用Mongoose的数组操作符即可实现：

编辑回复

// 编辑指定帖子下的指定回复
const editReply = async(req, res) => {
    try {
        const { postId, replyId, newText } = req.body;
        await Post.findOneAndUpdate(
            { _id: postId, 'replies._id': replyId }, // 定位目标帖子与回复
            { $set: { 'replies.$.text': newText } }, // $表示匹配到的数组元素
            { new: true }
        )
        res.status(200).json({msg: '回复编辑成功'})
    } catch (err) {
        console.log(err)
        res.status(500).json({msg: '编辑失败'})
    }
}

删除回复

// 删除指定帖子下的指定回复
const deleteReply = async(req, res) => {
    try {
        const { postId, replyId } = req.body;
        await Post.findOneAndUpdate(
            { _id: postId },
            { $pull: { replies: { _id: replyId } } }, // 从数组中移除指定ID的回复
            { new: true }
        )
        res.status(200).json({msg: '回复删除成功'})
    } catch (err) {
        console.log(err)
        res.status(500).json({msg: '删除失败'})
    }
}

内容的提问来源于stack exchange，提问作者khayal