angular 5 template forms detect change of form validity status : <p>are <a href="https://angular.io/guide/reactive-forms#observe-control-changes" rel="noreferrer">reactive forms</a> the way to go in order to have a component that can listen for changes in the validity status of the form it contains and execute some compoment's methods?</p>

<p>It is easy to disable the submit button in the template using templateRef like <code>[disabled]="#myForm.invalid"</code>, but this does not involve the component's logic.</p>

<p>Looking at <a href="https://angular.io/guide/forms" rel="noreferrer">template forms' doc</a> I did not find a way </p>
