Include only the path of Mongoose schema which is relevant to value of another path

Question

Let's say I have a Schema like this:

Schema({
    username: String,
    privilege: {
        type: String,
        enum: ["admin", "pro", "user", "guest"],
        required: false,
        default: "user"
    },
    tagType: { // A little badge that appears next to users' names on the site.
        ///???
    }
});

For the tagType, I would like to be able to define something like this if privilege is admin:

{
    color: String,
    image: String,
    text: {
        type: String,
        required: true,
        enum: ["I'm the highest rank", "I'm an admin", "Admin privileges are great"]
    },
    dateAdded: Date
}

Meanwhile, if privilege is pro:

{
    color: String,
    text: {
        type: String,
        required: false,
        enum: ["This website is great", "I'm am a Pro user", "I get a nice tag!"],
        default: "This website is great"
    },
    dateAdded: Date
}

Meanwhile, for all user or guest entries, no option should be allowed.

Is this sort of dynamic cross-checking possible? I have tried reading through the docs, but despite things that seem much more complex being in there, I couldn't find any way to achieve this.

Answer 1

You can implement this by using Discriminators

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

const userSchema = new Schema(
  {
    username: String,
    privilege: {
      type: String,
      enum: ["admin", "pro", "user", "guest"],
      required: false,
      default: "user"
    }
  },
  { discriminatorKey: "privilege" }
);

const User = mongoose.model("User", userSchema);

User.discriminator(
  "admin",
  new Schema({
    tagType: {
      color: String,
      image: String,
      text: {
        type: String,
        required: true,
        enum: ["I'm the highest rank","I'm an admin","Admin privileges are great"]
      },
      dateAdded: { type: Date, default: Date.now }
    }
  })
);

User.discriminator(
  "pro",
  new Schema({
    tagType: {
      color: String,
      text: {
        type: String,
        required: false,
        enum: ["This website is great","I'm am a Pro user","I get a nice tag!"],
        default: "This website is great"
      },
      dateAdded: { type: Date, default: Date.now }
    }
  })
);

module.exports = User;

With this model and schema you can create a user with tagType it will be ignored.

Sample code to create user:

const User = require("../models/user");

router.post("/user", async (req, res) => {
  let result = await User.create(req.body);
  res.send(result);
});

Sample request body:

{
    "username": "user 1",
    "tagType": {
        "color": "red",
        "text": "I'm an admin"
    }
}

Response:

{
    "privilege": "user",
    "_id": "5dfa07043a20814f80d60d6b",
    "username": "user 1",
    "__v": 0
}

Sample request to create an admin: (note that we added "privilege": "admin")

{
    "username": "admin 1",
    "privilege": "admin",
    "tagType": {
        "color": "red",
        "text": "I'm an admin"
    }
}

Response: (note that tagType is saved)

{
    "_id": "5dfa07a63a20814f80d60d6d",
    "privilege": "admin",
    "username": "admin 1",
    "tagType": {
        "color": "red",
        "text": "I'm an admin",
        "dateAdded": "2019-12-18T11:04:06.461Z"
    },
    "__v": 0
}