Conditional Validation in Ember

Often in real world applications you’ll find yourself needing to set up conditional validation rules. e.g. Require this if that === “foo”. The Ember Changeset Conditional Validations addon adds this functionality to Ember Changeset Validations.

In our quick example we have a form to request a extension to some homework. Our model has two fields

• reason
• notes

Reason is an enum containing many common excuses e.g.

• Dog ate it
• Illness
• Couldnt find it
• Internet was down
• Lost it in the great Mt. Gox hack of 2014
• Other

The reason field is required. If the user selects other we also want to make sure the notes field is required.

// app/validations/extension-request.js

import {
  validateLength,
  validatePresence,
} from "ember-changeset-validations/validators";
import validateSometimes from "ember-changeset-conditional-validations/validators/sometimes";

export default {
  reason: [validatePresence(true)],
  notes: validateSometimes(
    [validatePresence(true), validateLength({ min: 32 })],
    function (/*changes, content*/) {
      // This isnt ember's get - it's implemented by ember-changeset-conditional-validations
      // so we will silence the lint error

      /* eslint-disable ember/no-get */
      return this.get("reason") === "other";
    }
  ),
};

validateSometimes() takes 2 arguments. The first is a validator or an array of validators you want applied to the attribute. The second argument is a callback function which represents the condition. If the condition callback returns true, the rules will be added.

View the addons readme for more examples.