TIL: Eloquents "sync" will return added and removed items

If you have used Laravel you are probably familiar with the "sync" method you can call on a relationship.

For example when you have a "Book" and "Category" model you can quickly sync the categories that are linked to a book based on what the user selected:

public function update(Request $request, Book $book) {
    $book->categories->sync($request->categories);
}

Today I learned it's really easy to check which items were removed and which were added to the relationship:

public function update(Request $request, Book $book) {
    $results = $book->categories->sync($request->categories);
    ray($results);
}

Pretty neat and usefull if you ask me!