Detach doesn't trigger cascade - php

Question

I have a many to many relationship. The pivot model hasMany children. When I call detach on the many to many, I need to also delete the pivot model's children. I wanted to use onDelete('cascade'), but that doesn't seem to work. I also tried this: http://laravel-tricks.com/tricks/using-model-events-to-delete-related-items, but that doesn't seem to work either. Neither are working probably because the destroy event is not being triggered.
Any ideas on how I can get the children to delete when I call detach?
Here's some of my code in case I made a mistake:
My pivot model:
Schema::create('beer_distributions', function(Blueprint $table)
{
$table->increments('id');
$table->integer('beer_id');
$table->integer('distributor_id');
The pivot model's children:
Schema::create('kegs', function(Blueprint $table)
{
$table->increments('id');
$table->integer('beer_distribution_id');
$table->dropForeign('kegs_beer_distribution_id_foreign');
$table->foreign('beer_distribution_id')
->references('id')
->on('beer_distributions')
->onDelete('cascade');
I don't know if there is anyway to salvage this approach. I called sync and then tried to delete the children, not realizing the parent was already gone making the children inaccessible.:
$attachments = $beer->distributors()->sync(Input::get('distributors'));
foreach ($attachments['detached'] as $distributor_id) {
BeerDistribution::where('beer_id', '=', $id)
->where('distributor_id', '=', $distributor_id)->first()->destroy();
}
UPDATE:
Just to be clear, I have four models I am working with. Beers and distributors with a many to many relationship. The pivot model, BeerDistributions, hasMany kegs. When I call sync to update a beers distributors, the BeerDistributions do get deleted automatically, and I want the kegs to get deleted at the same time.
Here are some of my models:
class Beer extends Eloquent {
public function distributors()
{
return $this->belongsToMany('Distributor', 'beer_distributions');
}
Beer ^ manyToMany with Distributor:
class Distributor extends Eloquent {
public function beers()
{
return $this->belongsToMany('Beer', 'beer_distributions');
}
The pivot model...
class BeerDistribution extends Eloquent {
public function kegs()
{
return $this->hasMany('Keg', 'beer_distribution_id');
}
has many kegs:
class Keg extends Eloquent {
public function beerDistribution()
{
return $this->belongsTo('BeerDistribution');
}

Answer 1

There seems to be some confusion here about pivot tables, detach, and cascades.
Basically, the detach method should be all you need for this. All it's doing is managing the pivot table through the belongsToMany() relationship.
So if you do $keg->distributors()->detach([1,2,3]) and $keg->id is 5, it will search and remove items from the pivot where the distributor is 1, 2, or 3 AND the keg id is 5. In most cases, you shouldn't even need an eloquent model for the pivot tables. detach(), attach(), and sync() will handle that table for you.
Delete on cascade is likely what is causing you issues because you have it backwards. In this case, the delete on cascade key would be put on the pivot table. What this means is when you delete a parent (keg or distribution), those items belonging to that parent in the pivot table would automatically be removed. This saves you from having orphaned data in the table.
Why I say you are doing this backwards is because you put the key on your kegs table which means when an item in the pivot table is deleted, your keg is also deleted. This is bad and not at all what you want. You want to delete items from the pivot table when your keg is deleted.
Remove that key and in your schema to create the beerDistributions add two keys that will look something like this...
$table->foreign('beer_id')->references('id')->on('beers')->onDelete('Cascade');
$table->foreign('distribution_id')->references('id')->on('distributors')->onDelete('Cascade');
And if you have a key which is deleting on cascade on your distributor's table, remove that too. Should only have those foreign keys on the pivot table.
Edit: Seeing as how you want to delete kegs, it looks as though you are referencing the wrong columns in the pivot table.
$table->foreign('id')
->references('beer_distribution_id')
->on('beer_distributions')
->onDelete('cascade');