尝试将对象推入MongoDB和Nodejs中的数组时，为什么会出现castError？

Question

I have a mongoDB and I am trying to make a Nodejs server to manipulate the data in the database. I get a castError when I try to push a Comment to the Comments array in a BlogPost object.

Source code below, please tell me if you're missing important information. Thanks in advance!

The route:

routes.post('/comments/push/:id', function(req, res) {
const blogPostId = req.param('id');
const commentProps = req.body;

BlogPost.findById(blogPostId)
  .then((blogPost) => {
    blogPost.comments.push(commentProps);
    return blogPost.save();
  })
    .then((blogPost) => res.status(200).json({
    'status': 'Comment is deleted.',
    'comment': blogPost
}))
.catch((error) => res.status(400).json(error)) });

The BlogPost schema:

const BlogPostSchema = new Schema({
content: {
type: String,
validate: {
  validator: (content) => content.length > 5,
  message: 'Content must contain at least 6 characters.'
},
required: [true, 'Content must be filled in.']
},
rating: Number,
user: { type: Schema.Types.ObjectId, ref: 'user' },
board: {type: Schema.Types.ObjectId, ref: 'board'},
comments: [{
  type: Schema.Types.ObjectId,
  ref: 'comment'
  }]
});

The Comment schema:

const CommentSchema = new Schema({
content: {
type: String,
validate: {
  validator: (content) => content.length > 5,
  message: 'Content must contain at least 6 characters.'
},
required: [true, 'Content must be filled in.']
},
user: { type: Schema.Types.ObjectId, ref: 'user' },
rating: Number

// board: Board
});

Here is the error in postman: postman screen

Help would be greatly appreciated!

Answer 1

1. first make sure what's you are receiving in req.body, it's not good to store directly from req.body.
2. second ref. comments Schema aspect a objectId while req.body is Object itself. i'm not sure what are you going to do but it something like blogPost.comments.push(req.body.someValidId);

third why 2 queries for simple update. you can use $push, $addToSet to push directly to comments or $pull to remove from comments.

BlogPost.findOneAndUpdate({
    _id:blogPostId
}, {
    $addToSet:{
        comments : someValidId
    }
}, {
    new :true,
    upsert:false
})
.then((blogPost) => {
    res.status(200).json({
        'status': 'Comment is deleted.',
        'comment': blogPost
    })
})
.catch((error) => 
    res.status(400).json(error)) 
});