Composer custom field validation

[Sebastián Cisneros]

I already created a custom field in the composer, and is working perfect. Now I want to add some validation, just like the one nodebb core has when you try to publish a topic without a title and you get this alert.

How can trigger this same alert with a different message and avoid the composer to submit (until this field validates)?

[baris]

Use 'filter:composer.check'

hooks.on('filter:composer.check', function (payload) {
     payload.error = 'sorry you can not post now';
     return payload;
});