firefly-iii/app/Providers/EventServiceProvider.php

<?php namespace FireflyIII\Providers;

use FireflyIII\Models\Account;
use FireflyIII\Models\Transaction;
use FireflyIII\Models\TransactionJournal;
use Illuminate\Contracts\Events\Dispatcher as DispatcherContract;
use Illuminate\Foundation\Support\Providers\EventServiceProvider as ServiceProvider;

/**
 * Class EventServiceProvider
 *
 * @package FireflyIII\Providers
 */
class EventServiceProvider extends ServiceProvider
{

    /**
     * The event handler mappings for the application.
     *
     * @var array
     */
    protected $listen
        = [
            'event.name'                => [
                'EventListener',
            ],
            'App\Events\JournalDeleted' => [
                'App\Handlers\Events\JournalDeletedHandler@handle',
            ],
        ];

    /**
     * Register any other events for your application.
     *
     * @param  \Illuminate\Contracts\Events\Dispatcher $events
     *
     * @return void
     */
    public function boot(DispatcherContract $events)
    {
        parent::boot($events);

        TransactionJournal::deleted(
            function (TransactionJournal $journal) {

                /** @var Transaction $transaction */
                foreach ($journal->transactions()->get() as $transaction) {
                    $transaction->delete();
                }
            }
        );

        Account::deleted(
            function (Account $account) {

                /** @var Transaction $transaction */
                foreach ($account->transactions()->get() as $transaction) {
                    $journal = $transaction->transactionJournal()->first();
                    $journal->delete();
                }
            }
        );

    }

}