How to change an entry's slug on EVENT_AFTER_SAVE_ELEMENT?

Question

My entries' titles are auto-generated from several fields values on first save.

When one of these fields values change, I would like to update the auto-generated slug also:

Event::on(
    \craft\services\Elements::class,
    \craft\services\Elements::EVENT_AFTER_SAVE_ELEMENT,
    function (Event $event) {
        $entry = Entry::find()
            ->id($event->element->id)
            ->one();

        if ([] !== $entry) {
            $title = craft\helpers\StringHelper::toAscii($entry->id.'-'.$entry->title);
            $title = craft\helpers\StringHelper::toLowerCase($title);
            $title = str_replace(' ', '-', $title);

            // 👷 I tried this below, but none works
            $entry->slug = $title; // ⬅️ Not working
            $entry->setFieldValue('slug', $title); // ⬅️ Error
            Craft::$app->elements->saveElement($entry); // ⬅️ Infinite loop
            $event->element->slug = $event->element->id; // ⬅️ Not working
        }
    }
);

Unfortunately, none of these methods works. Any idea how to achieve this?

Answer 1

You can change the value in the DB directly instead of using the Elements service

$entry = $event->element;
$elementId = $entry->id;
$siteId = $entry->siteId;
Craft::$app->getDb()->createCommand()
    ->update(
        '{{%elements_sites}}',
        ['slug' => ElementHelper::createSlug('new-slug')],
        [
            'elementId' => $elementId,
            'siteId'    => $siteId
        ]
    )->execute();

By the way the following condition [] !== $entry won't be any good when you fetch an element with one() because one returns an object of instance ElementInterface or null but never an empty array. You can check !== null instead and if you fetch things via all you can perform an empty check if( empty($entries) === false)

Answer 2

Another shorter and probably slightly more performant solution, using EVENT_BEFORE_SAVE:

/*
* Automatically update Element slugs to match the title if updated.
*/
Event::on(
    Element::class,
    Element::EVENT_BEFORE_SAVE,
    function(craft\events\ModelEvent $event) {
        $entry = $event->sender;
        $entry->slug = ElementHelper::createSlug($entry->title);
    },
    false
);

Answer 3

I finally use this simple solution, which works pretty fine:

Event::on(
    Element::class,
    Element::EVENT_BEFORE_SAVE,
    function(craft\events\ModelEvent $event) {
        $entry = $event->sender;
        if (!\craft\helpers\ElementHelper::isDraftOrRevision($entry)) {
            if (!empty($entry->id)) {
                $entry->slug = $entry->title;
            }
        }
    },
    false
);

Where $entry->slug = $entry->title syncs the slug to the title if the entry is not new (!empty($entry->id)).

UPDATE:

$entry->slug = ($entry->title !== null) ? \craft\helpers\StringHelper::slugify($entry->title) : $entry->slug;

This prevents to get a wrong slug on first save.