Mongo schema, array of string with unique values

Question

I'm creating the schema for a mongo document and I can do everything except prevent duplicates in a non-object array.

I'm aware of the addToSet, but I'm referring to Mongo Schema.

I don't want to check on Update using $addToSet, rather I want this to be part of my schema validation.

Example below.

let sampleSchema = {
   name: { type: 'String', unique: true },
   tags: [{ type: 'String', unique: true }]
}

The above snippet prevents name from having duplicate values. It allows tags to be stored as a string array.

But.. I cannot limit the array to be unique strings.

{ name: 'fail scenario', tags: ['bad', 'bad', 'array']}

I'm able to insert this record which should be a fail scenario.

Possible duplicate of [Mongoose Unique values in nested array of objects](http://stackoverflow.com/questions/15921700/mongoose-unique-values-in-nested-array-of-objects) — Karlen, Jan 22 '17 at 08:44
I'm aware of the $addToSet, but I'm referring to Mongo Schema. — Proximo, Jan 22 '17 at 13:13

Med Lazhari · Accepted Answer · 2020-07-11T18:08:16.697

8

const express = require('express');
const router = express.Router();
const mongoose = require('mongoose');
const _ = require('underscore');

let sampleSchema = new mongoose.Schema({
  name: {
    type: 'String',
    unique: true
  },
  tags: [{
    type: 'String'
  }]
})
sampleSchema.pre('save', function (next) {
  this.tags = _.uniq(this.tags);
  next();
});
const Sample = mongoose.model('sample', sampleSchema, 'samples');


router.post('/sample', function (req, res, next) {
  const sample = new Sample(req.body);

  sample.save()
    .then((sample) => {
      return res.send(sample);
    })
    .catch(err => {
      return res.status(500).send(err.message);
    })
});

edited Jul 11 '20 at 18:08

answered Jan 22 '17 at 13:30

Med Lazhari

588
4
9

Thanks for the answer but I'm trying to do this with only Schema, not code and not with flags on save, update methods of mongoose. – Proximo Jan 22 '17 at 14:10
In underscore, it's _.uniq not _.unique. Also, here is a revised version that works with references: `this.tags = _.uniq(this.tags, function(i) {return (i._id) ? i._id.toString() : i;});` – BuffMcBigHuge Aug 08 '17 at 17:10

Proximo · Answer 2 · 2017-01-22T15:27:14.387

4

I've come to the conclusion that this is impossible to do via Mongoose Schema.

JSON schema is done like so.

let schema = {
   name: { type: 'string' }
   tags: { 
      type: 'array',
      items: { type: 'string', uniqueItems: true }
   }
}

I'll validate with JSON schema before creating Mongo Document.

edited Jan 22 '17 at 15:27

answered Jan 22 '17 at 15:22

Proximo

5,566
8
45
63

score 2 · Answer 3 · answered Aug 08 '17 at 17:19

This method builds on Med's answer, handles references, and done completely in scheme validation.

let sampleSchema = new mongoose.Schema({
    strings: [{type: 'String'}],
    references: [{type: mongoose.Schema.Types.ObjectId, ref: 'Reference'],
});

sampleSchema.pre('save', function (next) {

    let sample = this;

    sample.strings = _.uniq(sample.strings, function(i) {return (i._id) ? i._id.toString() : i;});
    sample.references = _.uniq(sample.references, function(i) {return (i._id) ? i._id.toString() : i;});

    return next();

});

Mongo schema, array of string with unique values

3 Answers3

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