BelongsToMany: Multi-Select and Relation Managers

Now, let's see how we can add data to a many-to-many relationship. Let's say that our Product may have many Tags.

For Tags, I've created a simple Model with one field, seeded a few tags, and then generated this simple Filament Resource:

php artisan make:filament-resource Tag --simple --generate

The result is this:

But, of course, it's not the topic of this lesson. What we need to do is add tags to products. Multiple tags.

The relationship in Eloquent is this:

app/Models/Product.php:

use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 
class Product extends Model
{
    // ...
 
    public function tags(): BelongsToMany
    {
        return $this->belongsToMany(Tag::class);
    }
}

There are a few ways to do it.

Option 1. Just Attach: Select Multiple

Let's add one more field in the form of ProductResource.

app/Filament/Resources/ProductResource.php:

return $form
    ->schema([
        // ...
        Forms\Components\Select::make('category_id')
            ->relationship('category', 'name'),
        Forms\Components\Select::make('tags') 
            ->relationship('tags', 'name') 
            ->multiple(), 
    ]);

Yes, that's it, all you need to do is add ->multiple() to the Select field, and it becomes a multi-select!

It also includes a search with auto-complete by default. Here's how it looks:

Option 2. Create and Attach: Relation Managers

Filament also offers a function to create a related record immediately...