Loopback: How to control document do not get or add additional property in loopbak?

[eramsa]

I have a registration model in loopback over mongodb with fallowing properties:

    "properties": {
        "Fname": {
          "type": "string",
          "required": true
        },
        "Lname": {
          "type": "string",
          "required": true
        },
        "phone": {
          "type": "string",
          "required": true
        },
        "date": {
          "type": "string",
          "required": true
        },
        "time": {
          "type": "string",
          "required": true
        }
      }

in application I post some additional data with model required data, for controlling and processing in server side:

```
submitForm() {

    let headers = new Headers(
      {
        'Content-Type': 'application/json'
      });
    let options = new RequestOptions({ headers: headers });

    let data = JSON.stringify({
      Fname: this.form.Fname,
      Lname: this.form.Lname,
      phone: this.form.phone,
      time: this.form.time,
      date: this.form.date,
      uid: this.form.uid
    });
    //console.log(data);

    let url = 'http://localhost:3000/api/registrations';

    return new Promise((resolve, reject) => {
      this.http.post(url, data, options)
        .toPromise()
        .then((response) => {
          console.log('API Response : ', response.status);
          resolve(response.json());
        })
        .catch((error) => {
          console.error('API Error : ', error.status);
          console.error('API Error : ', JSON.stringify(error));
          reject(error.json());
        });
    });
  }

In server side I have this code:

     Registration.observe('before save', function (ctx, next) {
        ```
    if (ctx.instance) {
                // When Create (POST)
                // ctx.instance have the json properties
                console.log("Triggers when create");
                if (checkUID(ctx.instance) ==200 ){
                    console.log('ok');
                }
            } else {
                // When Update (UPDATE)
                // ctx.data have the json properties
                console.log("Triggers when update");
            }
            next();
        });

but after successfully registration I saw that uid that was added into document and regardless to model's properties, document contains addition properties.

    {
        "Fname": "Eram",
        "Lname": "SA",
        "phone": "1234567890",
        "date": "2017/10/06",
        "time": "17:37:46",
        "id": "59d78e3f5e5e6704205038aa",
        "uid": "38bc3241a43073a7b40d186f24923cc5"
      },

[osamasaeed]

use strict:true in your model properties

{
  "name": "Customer",  // See Top-level properties below

  "description": "A Customer model representing our customers.",
  "base": "User",
  "idInjection": false,
  "strict": true,
. . . 
}

[parsarian]

Dear @osamasaeed by using strict:true there is problem happening that says :`uid is not defined in the modelhoweveruid` is not defind in registration model but we need this uid on server side to verify the new registration.

[osamasaeed]

If you just want to use 'uid' attribute then you can remove it after verify in the beforeRemote hook e.g
in myModel.js

. . . 
Mymodel.beforeRemote('create',function(context, data, next){
// verifying 
...
// after verify
  delete data.uid
  return next();
})
. . .

There are many remote hooks you can find on loopback documentation
https://loopback.io/doc/en/lb3/Remote-hooks.html
more detail about accessing relational model Remotehooks
https://loopback.io/doc/en/lb2/Accessing-related-models.html
to use these relational model remote hooks use prefix "prototype." for example

Mymodel.beforeMethod("prototype.__get__relatedModelName",function(ctx,data,next){
next()
})

[eramsa]

I got solution from your guiding,
I've add a variable for UID after storing it. removed attribute by

UID = ctx.instance.uid;
ctx.instance.unsetAttribute('uid');