Mongodb 仅针对特定字段更新数组

Question

I have a json array reorderList for a topic:

const reorderList = [
    { _id: '5e6b419c76a16d5c44d87132', order: 0 },
    { _id: '5e6b41a276a16d5c44d87139', order: 1 },
    { _id: '5e6b41a776a16d5c44d87140', order: 2 }
]

And my TopicSchema is like this:

var TopicSchema = new Schema({
    topicTitle: String,
    topicQuestion: [
        {           
            questionTitle: String,
            answer: String,
            order: Number
        }
    ]
}

Now I want to update my topic questions order based on the reorderList's _id .

But the below statement will replace all the things from topicQuestion (eg questionTitle and answer will be removed)

Topic.findOneAndUpdate(
    { '_id': topicId },
    { $set: { 'topicQuestion': reorderList } }, //replaces here
    { upsert: true },
    function (err, response) {
         ...
    });

How to update it based on reorderList and also keep the original data inside topicQuestion?

Answer 1

The schema that you're using is badly designed. What you can do here is create another schema, TopicQuestionSchema and put a ref to the topic it belongs to.

var TopicQuestionSchema = new Schema({          
    questionTitle: String,
    answer: String,
    order: Number,
    topic: {type: ObjectId, ref: 'Topic'} // the name of your model
}

This way you can still keep track of the topic the questions belong to, and still be able to update the order easily.