What is the difference between syncWithoutDetaching and attach in Laravel?
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3 Answers
Let's assume that you have auto-increment primary key id in your pivot table, you will notice:
attach()will add the new records to the pivot table, and pre-existed relations will get fresh ids.sync()will remove all existed relations and set only provided in current request, with fresh ids too.syncWithoutDetaching()will not remove all existing relations missing from the one provided in current process, then the pre-existed rows won't get new ids.
Comments
Two things:
attach()will always add a new record to the pivot table, whereassyncWithoutDetaching()will only add a new record if one does not exist.
Let's say you have orders and items.
$order->items()->attach(1);
$order->items()->attach(1);
// $order->items()->count() === 2
$order2->items()->syncWithoutDetaching(1);
$order2->items()->syncWithoutDetaching(1);
// $order2->items()->count() === 1
attach()returnsnull, whereassyncWithoutDetaching()returns an array showing what was attached/detached/updated.
Comments
attach() will add new records even if they already exist.
sync() will remove records that don't exist in the sync(), leave untouched those that already do, and add the ones that don't.
syncWithoutDetaching() is the same as sync() but doesn't remove anything.
So
1: Apple, 2: Banana, 3: Carrot
attach(['Apple', 'Date']) -> 1: Apple, 2: Banana, 3: Carrot, 4: Apple, 5: Date
Note: there are two Apples
but
sync(['Apple', 'Date']) -> 1: Apple, 4: Date
and
syncWithoutDetaching(['Apple', 'Date']) -> 1: Apple, 2: Banana, 3: Carrot, 4: Date
sync(Array, false) is the same as syncWithoutDetaching():
public function syncWithoutDetaching($ids)
{
return $this->sync($ids, false);
}
In short, by default sync() detaches.
