laravel model relation not working - laravel

Question

I have created a laravel api for my application.I have used Pingpong module package for different modules.I am having hard time establishing many-to-many relation.I have 3 tables:roles,groups,group_roles.And my models are:
Group.php
namespace Modules\User\Entities;
use Illuminate\Database\Eloquent\Model;
class Group extends Model {
protected $fillable = [];
protected $table='groups';
public static function roles(){
return $this->belongsToMany('Modules\User\Entities\Role','group_roles','group_id','role_id');
}
}
Role.php
namespace Modules\User\Entities;
use Illuminate\Database\Eloquent\Model;
class Role extends Model {
protected $fillable = [];
protected $table='roles';
public function groups(){
return $this->belongsToMany('Modules\User\Entities\Group','group_roles','group_id','role_id');
}
}
And my controller
namespace Modules\User\Http\Controllers;
use Pingpong\Modules\Routing\Controller;
use Modules\User\Entities\Group;
use Modules\User\Entities\Role;
use Illuminate\Http\Request;
use App\Login;
use Input;
use Validator;
use Hash;
use Response;
class UserController extends Controller {
public function getGroupById(Request $request){
$groups=Group::with('roles')->get();
return Response::json ([
'status'=>'ok',
'group'=>$groups
],200);
}
}
The problem is I am not able to establish the relation between the models and the getGroupById returns 500 internal error response.$group=Group::all(); $group=Group::find($request['id']); returns fine but it is not returning related roles.
Similar structure and codes work fine on app without the use pingpong.

Answer 1

Your relationships are currently like this:
// not sure why this is static?
public static function roles(){
return $this->belongsToMany('Modules\User\Entities\Role', 'group_roles', 'group_id', 'role_id');
}
public function groups(){
return $this->belongsToMany('Modules\User\Entities\Group', 'group_roles', 'group_id', 'role_id');
}
Please note from the docs, regarding the belongsToMany method:
The third argument is the foreign key name of the model on which you are defining the relationship, while the fourth argument is the foreign key name of the model that you are joining to...
So with this in mind I think your relationships may be incorrect due to using the wrong arguments on your belongsToMany method calls. I think it should be like this:
public function roles(){
return $this->belongsToMany('Modules\User\Entities\Role', 'group_roles', 'group_id', 'role_id');
}
public function groups(){
return $this->belongsToMany('Modules\User\Entities\Group', 'group_roles', 'role_id', 'group_id');
}
Also if you have intermediate table columns you'd need to declare those on the belongsToMany call.
Hope that helps!
Edit
Firstly, you said getGroupById returns 500 internal error response. Have you tried checking what the actual error is!? 500 internal error doesn't provide much info, I'm sure you'd get to the bottom of things a lot faster if you found out the exact issue through laravel's usual error response page.
I assume you're doing this through an ajax request so you could use the network tab if you're using chrome then click on the 500 request to see the error laravel returns or you can use something like postman and hit the url through that.
If I wanted to quickly check the functionality of the models relationship methods, I'd do the following:
After setting up some data for a group and relationship, could you try running this in tinker or a route for testing/debugging.
$g = Group::first(); // get the first group, or you could use find($id) if you had a specific group in mind
// if you're in tinker
$g->roles; // show the roles
// if you're running on a route
dd($g->roles); // show the roles

Answer 2

While haakym's answer is very detailed, but you can also try changing your mapping table name to convention based 'group_role' instead of 'group_roles'. With this method you will have to supply only one argument to belongsToMany call.
Note that in general it should not matter if the other arguments are correct, but its just another step to debug!