Javascript 带Ref的Mongo架构：未使用保存更新文档

我有一个博客，我正在尝试为用户添加添加评论的功能。我已经参照我的

博客

模型创建了一个

评论

模型。当我试图在Postman中将评论添加到

博客

时，它会将

评论

保存在评论文档中，但不会将相关的

评论

添加到我的

博客

文档中。我希望我的文档中的博客项目有自己的评论字段，每个评论都有

评论模式

const commentSchema = mongoose.Schema({
  comment: { type: String, required: true },
  blog: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Blog"
  }
});

commentSchema.set("toJSON", {
  transform: (document, returnedObject) => {
    returnedObject.id = returnedObject._id.toString();
    delete returnedObject._id;
    delete returnedObject.__v;
  }
});

module.exports = mongoose.model("Comment", commentSchema);

const blogSchema = mongoose.Schema({
  title: { type: String, required: true },
  author: { type: String, required: true },
  url: String,
  likes: Number,
  user: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "User"
  },
  comments: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Comment"
  }
});

blogSchema.set("toJSON", {
  transform: (document, returnedObject) => {
    returnedObject.id = returnedObject._id.toString();
    delete returnedObject._id;
    delete returnedObject.__v;
  }
});

博客模式

const commentSchema = mongoose.Schema({
  comment: { type: String, required: true },
  blog: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Blog"
  }
});

commentSchema.set("toJSON", {
  transform: (document, returnedObject) => {
    returnedObject.id = returnedObject._id.toString();
    delete returnedObject._id;
    delete returnedObject.__v;
  }
});

module.exports = mongoose.model("Comment", commentSchema);

const blogSchema = mongoose.Schema({
  title: { type: String, required: true },
  author: { type: String, required: true },
  url: String,
  likes: Number,
  user: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "User"
  },
  comments: {
    type: mongoose.Schema.Types.ObjectId,
    ref: "Comment"
  }
});

blogSchema.set("toJSON", {
  transform: (document, returnedObject) => {
    returnedObject.id = returnedObject._id.toString();
    delete returnedObject._id;
    delete returnedObject.__v;
  }
});

我尝试添加新注释的Express代码

blogsRouter.post("/:id/comments", async (request, response, next) => {
  try {
    const blog = await Blog.findById(request.params.id);
    console.log("Blog", blog);
    const comment = new Comment({
      comment: request.body.comment,
      blog: blog._id
    });
    const result = await comment.save();
    console.log("Blog Comments", blog.comments);
    blog.comments = blog.comments.concat(result._id);
    await blog.save();
    response.status(201).json(result.toJSON());
  } catch (error) {
    next(error);
  }
});

在邮递员中提交到该路线时，上述代码会导致以下错误：

TypeError: Cannot read property 'concat' of undefined

如下图所示，评论很好地通过，并保存到评论文档中的数据库中，但没有填充博客文档，因此我想为什么会出现此错误

---

请注意，我正在为博客填充Get和Put路由中的用户和评论。如果需要，我可以发布，可能有问题

我想你是想在

blogSchema

和

commentSchema

之间建立一对多的关系。这意味着您需要修改

博客架构中的
注释
：

const blogSchema = mongoose.Schema({
    title: { type: String, required: true },
    author: { type: String, required: true },
    url: String,
    likes: Number,
    user: {
        type: mongoose.Schema.Types.ObjectId,
        ref: "User"
    },
    comments: [
        {
            type: mongoose.Schema.Types.ObjectId,
            ref: "Comment"
        }
    ]
});

这将允许您使用
concat
或
push
如下所示：

blog.comments.push(comment);

结果应该是一样的