As you probably know, you can use the attach() method to relate two models within a BelongsToMany relationship. The only problem with attach() is that it doesn’t check to see if the relationship already exists. So, essentially, you could attach the same model more than once to a relationship, which isn’t ideal.
For instance, you have pizzas and ingredients.
You could always do something like this:
$relationship = $pizza->ingredients()->where('ingredient_id', $ingredient->id)->get();
if(!$relationship)
{
$pizza->ingredients()->attach($ingredient);
}
Or, you could use this method, which checks if the relationship exists and it doesn’t double up:
$pizza->ingredients()->syncWithoutDetaching($ingredient);
What this will do is sync the ingredient with the pizza (like the sync() method), however, if the relationship already exists, it won’t do anything. The relationship will stay, and nothing else will detach.
