How to register a default Observer for every Model instance with Laravel

Laravel 5.1

I'm trying to register a single model observer for every Model that extends my AbstractModel (who are extending Illuminate\Database\Eloquent\Model).

The problem is my GenericModelObserver can't listen to events fired by Models inheriting AbstractModel.

Let me show what I did so far.

A Service Provider was created and put on the last position of the providers array inside config/app.php

<?php

// app/Providers/ObserverServiceProvider.php

namespace App\Providers;

use App\Models\Quotation;
use App\Models\AbstractModel;
use App\Observers\QuotationObserver;
use App\Observers\GenericModelObserver;
use Illuminate\Support\ServiceProvider;

class ObserverServiceProvider extends ServiceProvider
{

    public function boot()
    {
        AbstractModel::observe(GenericModelObserver::class);
        Quotation::observe(QuotationObserver::class);
    }

    public function register()
    {

    }
}

Then I have my plain simple GenericModelObserver

<?php

// app/Observers/GenericModelObserver.php

namespace App\Observers;

use App\Models\AbstractModel;

class GenericModelObserver
{
    public function saving(AbstractModel $model)
    {
        return $model->valid();
    }
}

The Abstract Model

<?php

// app/Models/AbstractModel.php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class AbstractModel extends Model
{
    // ...
}

My Quotation Model

<?php

// app/Models/Quotation.php

namespace App\Models;

class Quotation extends AbstractModel
{
    // ...
}

When Quotation is saved, the GenericModelObserver can't listen to the saving event or any other event.

The same applies for other Models that don't have a specific Model Observer.

Is this the right strategy? I would not like to bind a observer to every model through the boot method.

via Chebli Mohamed