Using existing HasMany relationships as HasOne in Laravel
A HasMany relationship in Laravel helps you to define a one-to-many relationship between two models. So, if you have a User model and a Post model, you can define a HasMany relationship between them like so.
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;
use App\Models\Post;
class User extends Model
{
public function posts(): HasMany
{
return $this->hasMany(Post::class);
}
}
And if you want to establish a one-to-one relationship between the User and Post models, you can use the HasOne relationship. So, you can define a HasOne relationship between the User and Post to retrieve the most popular post of a user using the ofMany() method like so.
public function popularPost(): HasOne
{
return $this->hasOne(Post::class)->ofMany('votes', 'max');
}
But in the latest version of Laravel…
You can now convert an existing
HasManyrelationship into aHasOnerelationship conveniently by chaining the newone()method to theHasManyrelationship.
So, if we were to use the HasMany relationship defined above, we can convert it into a HasOne relationship like so.
public function popularPost(): HasOne
{
return $this->posts()->one()->ofMany('votes', 'max');
}
The benefit of using the one() method is that you don’t have to repeat the same foreign key configuration across the relationship methods if you’re defining the foreign key in the HasMany relationship method.
Laravel’s DX for the win!
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