# Add validation to a smart field edition

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## Add validation to a smart field edition

**Context**: I want to make sure that my users can only enter a value satisfying a certain set of conditions when editing a smart field.

Here I'm working on a collection `customers` and the smart field `'must-be-kuku'` should only accept the value `kuku`.

{% embed url="<https://www.loom.com/share/22641b6c62d9469ea244e12b4557f02e>" %}

`forest/customers.js`

```jsx
const { collection } = require('forest-express-sequelize');
const models = require('../models');

// This file allows you to add to your Forest UI:
// - Smart actions: <https://docs.forestadmin.com/documentation/reference-guide/actions/create-and-manage-smart-actions>
// - Smart fields: <https://docs.forestadmin.com/documentation/reference-guide/fields/create-and-manage-smart-fields>
// - Smart relationships: <https://docs.forestadmin.com/documentation/reference-guide/relationships/create-a-smart-relationship>
// - Smart segments: <https://docs.forestadmin.com/documentation/reference-guide/segments/smart-segments>
collection('customers', {
  actions: [],
  fields: [
    {
      field: 'must-be-kuku',
      type: 'String',
      get(customer) {
        return 'kuku';
      },
      set(customer, value) {},
    },
  ],
  segments: [],
});
```

At the route level I need to check the user input from the edit form in the UI and check the value that has been entered into the field `'must-be-kuku'`.

`routes/customers.js`

```javascript
const express = require('express');
const { PermissionMiddlewareCreator } = require('forest-express-sequelize');
const { customers } = require('../models');

const router = express.Router();
const permissionMiddlewareCreator = new PermissionMiddlewareCreator(
  'customers'
);

// Update a Customer
router.put(
  '/customers/:recordId',
  permissionMiddlewareCreator.update(),
  (request, response, next) => {
    if (request.body.data.attributes['must-be-kuku'] !== 'kuku') {
      return response.status(403).send('should have been kuku!');
    }
    next();
  }
);

module.exports = router;
```