Infinite loop while listening model event

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I have an Laravel application for Properties, let's say somewhere in my code I do:

$property = new Property();
$property->city = "New York";
 ...
$property->save();

Then I have Event Listener that listens for specific event:

$events->listen(
    'eloquent.saved: Properties\\Models\\Property',
    'Google\Listeners\SetGeoLocationInfo@fire'
);

And finally in SetGeoLocationInfo.php I have

public function fire($event)
 {
    $property = $event;
    ...
    //get GPS data from Google Maps

    $property->latitude = $googleMapsObject->latitude;
    $property->longitude = $googleMapsObject->longitude;
    $property->save();
 }

And when I save model in goes to infinite recursion, because of save() evoked in the handler.

How I can change my code to make it fill location data just one time after saving and avoid recursion?

I cannot use flushEventListeners() because in this case other listeners stop working (e.g. property photo attaching).

I hit the same. In Laravel 5.6 you can simply override the finishSave() function in your model:

protected function finishSave(array $options)
{
    // this condition allow to control whenever fire the vent or not
    if (!isset($options['nosavedevent']) or empty($options['nosavedevent'])) {
        $this->fireModelEvent('saved', false);
    }

    if ($this->isDirty() && ($options['touch'] ?? true)) {
        $this->touchOwners();
    }

    $this->syncOriginal();
}

Then you can use it like this:

public function fire($event)
{
    $property = $event;
    ...
    //get GPS data from Google Maps

   $property->latitude = $googleMapsObject->latitude;
   $property->longitude = $googleMapsObject->longitude;
   $property->save(['nosavedevent' => true]);
}

Infinite loop when a model is updated in an event listener, and that , Infinite loop when a model is updated in an event listener, and that event is cuased by a preceding update on that same model. This code describes the state machine for a very basic car radio system. It is basically an infinite loop that reads incoming events. The state machine is only 2 states: radio mode, or CD mode. The event is either a mode change from radio to cd back and forth, or a go to next (next preset for radio or next track for CD).

In this case probably better would be using saving method. But be aware that during saving you should not use save method any more, so your fire method should look like this:

public function fire($event)
{
    $property = $event;
    ...
    //get GPS data from Google Maps

    $property->latitude = $googleMapsObject->latitude;
    $property->longitude = $googleMapsObject->longitude;
}

Other solution would be adding condition to to set and save GPS location only if it's not set yet:

if (empty($property->latitude) || empty($property->longitude)) {
    $property->latitude = $googleMapsObject->latitude;
    $property->longitude = $googleMapsObject->longitude;
    $property->save();
}

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Your Property save method (you must define property constants for it):

public function save($mode = Property::SAVE_DEFAULT)
{
    switch ($mode) {
        case Property::SAVE_FOO:
            // something for foo
        break;
        case Property::SAVE_BAR:
            // something for bar
        break;
        default:
            parent::save();
        break;
    }
}

Call it:

public function fire($event)
 {
    $property = $event;
    ...
    //get GPS data from Google Maps

    $property->latitude = $googleMapsObject->latitude;
    $property->longitude = $googleMapsObject->longitude;
    $property->save(Property::SAVE_FOO);
 }

or

$property->save(); // as default

What good? All conditions are in one place (in save method).

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You can user forget() to unset an event listener.

Event::listen('a', function(){
    Event::forget('a');

    echo 'update a ';
    event("b");
});

Event::listen('b', function(){
    Event::forget('b');

    echo 'update b ';
    event("a");
});

event("a"); // update a update b

The model event keys are named as "eloquent.{$event}: {$name}" eg "eloquent.updated: Foo"

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Inside you're fire method, you could have it call $property->syncOriginal() before applying new attributes and saving.

Model classes have a concept of 'dirty' attributes vs. 'original' ones, as a way of knowing which values have already been pushed to the DB and which ones are still slated for an upcoming save. Typically, Laravel doesn't sync these together until after the Observers have fired. And strictly-speaking, it's an ant-pattern to have your Listener act like it's aware of the context in which it's fired; being that you're triggering it off the saved action and can therefore feel confident that the data has already reached the DB. But since you are, the problem is simply that the Model just doesn't realize that yet. Any subsequent update will confuse the Observer into thinking the original values that got you there are brand new. So by explicitly calling the syncOriginal() method yourself before applying any other changes, you should be able to avoid the recursion.

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Comments
  • when firing, use saving, instead of save
  • Just override save method in Property - pass argument for saving mode. In fire() like this: $property->save(Property::SAVE_FROM_GOOGLE_FIRE); for other something more.
  • This can't avoid recursion
  • @Deep Why do you think so? If you save only twice you won't have any recursion
  • Because properties (value, exists) can not be major/master for mode of save
  • Do you mean I have to listent for saving eloquent.saving: Exclusives\\Models\\Exclusive event? Other solution is not applicable because in case of of changing street address by user I have to find new coordinates.
  • @ademin Yes, I mean that, but it might not be reasonable also to update coordinates each time, you might get interested in getDirty method to update coordinates only if specific fields have been changed
  • Sorry, do you mean I should write directly to the DB instead of // something for foo ?
  • Yes, why not? You yourself have come to recursion. You have two ways: 1) rewrite without recursion 2) override the save method, and write in it all that is needed.
  • I don't know, it doesn't look like solution, it's more like a hack. I expected may be I could create custom event or pass some argument with event...
  • @ademin I agree. To be honest I have little skill in laravel. We'll wait together. Me also interest these opportunities laravel. But you must understand that this situation is a cause of poor application architecture design.
  • @ademin how are you? How you fix it?