I have a simple document with name (require), description (optional). In my model, I update a document with a valid id and I pass description with value undefined because I want to remove this property from document. However, I got following error:
**message=Cast to string failed for value "undefined" at path "description", name=CastError, type=string, value=undefined, path=description** . How do I remove description property on update when user does not provide description? Is it possible?

Thanks

```
/*jslint indent: 2, node: true, nomen: true*/

'use strict';

var Schema = require('mongoose').Schema;
var mongoose = require('mongoose');

var mongooser = require('../../lib/mongooser');

// Schema

var schema = new Schema({
  name: {
    required: true,
    set: mongooser.trimSetter,
    trim: true,
    type: String,
    unique: true
  },
  description: {
    set: mongooser.trimSetter,
    trim: true,
    type: String
  }
});

// Export

module.exports = mongoose.model('Role', schema);

```

**// Role.js**

```
var update = function (model, callback) {
    var test = { name: 'Users', description: undefined };

    RoleSchema.findByIdAndUpdate(model.id, test, function (error, role) {
      callback(error, role);
    });
};

```