Laravel/Ardent - on save(), error: Relationship method must return an object of type Illuminate

I'm having some trouble getting my Laravel relationships to work out. In my application, there is a one-to-many relationship between users and ideas. (A user may have multiple ideas.) I'm using Ardent.

Here's my User model:

 use Illuminate\Auth\UserTrait; use Illuminate\Auth\UserInterface; use Illuminate\Auth\Reminders\RemindableTrait; use Illuminate\Auth\Reminders\RemindableInterface; use LaravelBook\Ardent\Ardent; class User extends Ardent implements UserInterface, RemindableInterface { use UserTrait, RemindableTrait; /** * The database table used by the model. * * @var string */ protected $table = 'users'; /** * The attributes excluded from the model's JSON form. * * @var array */ protected $hidden = array('password', 'remember_token'); protected $fillable = array('first_name', 'last_name', 'email', 'password'); public $validation_errors; public $autoPurgeRedundantAttributes = true; public $autoHashPasswordAttributes = true; public $autoHydrateEntityFromInput = true; public static $passwordAttributes = array('password'); public static $rules = array( 'first_name' => 'required|between:1,16', 'last_name' => 'required|between:1,16', 'email' => 'required|email|unique:users', 'password' => 'required|between:6,100' ); public function ideas() { return $this->hasMany('Idea'); } } 

And here's my Idea model:

 use LaravelBook\Ardent\Ardent; class Idea extends Ardent { /** * The database table used by the model. * * @var string */ protected $table = 'ideas'; protected $fillable = array('title'); public $validation_errors; public $autoPurgeRedundantAttributes = true; public $autoHydrateEntityFromInput = true; public static $rules = array( 'title' => 'required' ); public function user() { return $this->belongsTo('User'); } } 

Finally, here's my controller code:

 class IdeasController extends BaseController { public function postInsert() { $idea = new Idea; $idea->user()->associate(Auth::user()); if($idea->save()) { return Response::json(array( 'success' => true, 'idea_id' => $idea->id, 'title' => $idea->title), 200 ); } else { return Response::json(array( 'success' => false, 'errors' => json_encode($idea->errors)), 400 ); } } } 

$idea->save() throws the error:

{ "error": { "type": "LogicException", "message": "Relationship method must return an object of type Illuminate\\Database\\Eloquent\\Relations\\Relation", "file": "\/var\/www\/3os\/vendor\/laravel\/framework\/src\/Illuminate\/Database\/Eloquent\/Model.php", "line": 2498 } } 

At first, I was trying to set the user_id in the Idea like so:

$idea->user_id = Auth::id(); 

I then changed it to:

$idea->user()->associate(Auth::user()); 

But the results were the same.

Any suggestions would be much appreciated.