Ensure unique field value in loopback model

Question

How to ensure uniqueness of a particular field in loopback model. Like below is the model Post, I have a field genericId in it, I want it to be unique in the database, and loopback to through an error, on duplicate key insertion.

{
  "name": "Post",
  "plural": "Post",
  "base": "PersistedModel",
  "properties": {
    "genericId": {
      "type": "string",
      "required":True 
    },
    "moderatedAt": {
      "type": "date"
    }
  },
  "validations": [],
  "acls": [],
  "methods": []
}

I have tried searching there documentation, and other examples but no success. One solution which I can think of is, to create a remoteHook for the create function, and validate this field before inserting, but looking for some other way.

Yes, Strongloop's LoopbackJS documentation is impossibly miserable. — Green, Nov 12 '15 at 08:18

Pandaiolo · Answer 1 · 2014-09-19T14:40:05.480

30

Not sure if it is the better way to achieve uniqueness, but you can find here the docs about indexing your model.

Just add a unique index on the field you want, and voila !

For your model, that would be :

{
  ...
    "genericId": {
      "type": "string",
      "required": True,
      "index": {"unique": true} 
    },
 ...
}

However, if the genericId field is the actual Id of the model, I suggest you declare it as such, so you can use findById method, and also avoid creation of a duplicate id field, which will happen if you don't declare any in your model.

{
  ...
    "genericId": {
      "type": "string", 
      "id": true,       // Ensure uniqueness and avoid another model id field
      "generated": true // Add this if you want Loopback to manage id content for you
    },
 ...
}

edited Sep 19 '14 at 14:40

answered Sep 19 '14 at 14:20

Pandaiolo

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Could you expend on "...declare it as such"? Thanks. – CNSKnight Dec 19 '16 at 17:54
*Note: this is an old post, not sure if its still valid*. In the above message, the code expands on the explanation : you declare a field as a model ID by setting the `id` prop (to `true`) in the field json definition. – Pandaiolo Dec 20 '16 at 18:34

score 28 · Accepted Answer · edited Sep 02 '16 at 18:00

28

Set validation rule in your common/models/post.js

Post.validatesUniquenessOf('genericId');

edited Sep 02 '16 at 18:00

Acapulco

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answered Nov 26 '14 at 12:23

IvanZh

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Thanks for the solution, but have already got it, sorry forgot to update it here. – Nishant Nov 27 '14 at 11:17
2

Correct validation docs https://docs.strongloop.com/display/APIC/Validating+model+data – EFernandes Jun 29 '16 at 16:31
5

Only supported connectors: In Memory, Oracle or MongoDB – EFernandes Jun 29 '16 at 16:32
2

What if I want to keep combination of fields to be unique? – Virendra Singh Rathore Nov 22 '16 at 06:39

Mathias Arens · Answer 3 · 2019-10-09T21:14:39.457

10

The Lookback v4 solution looks like this:

@model()
export class Client extends Entity {

  @property({
    type: 'string',
    required: true,
    index: {
      unique: true,
    },
  })
  name: string;

}

Then you must update your schema:

npm run migrate

or recreate it:

npm run migrate -- --rebuild

edited Oct 09 '19 at 21:14

answered Feb 10 '19 at 04:56

Mathias Arens

317
5
9

Did you update your schema? `npm run migrate` or `npm run migrate -- --rebuild`? – Mathias Arens Oct 09 '19 at 21:12
Not every connector might support this. I checked it for PostgreSQL. MySQL is supported, too, I guess. – Mathias Arens Oct 09 '19 at 21:20
Thank you Mathias, this is what I've been looking for. Tested in PostgreSQL. Btw, it doesn't send a good error message for the response. The error response now would only be 500. Does any of you have reference for editing that? Thank you! – Irfandy Jip Jul 02 '21 at 03:04
This answer is more elegant and also correct one for Mongo Driver, in my opinion – ddsultan Jan 19 '22 at 21:33

Ensure unique field value in loopback model

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