委托delete（）错误类名必须是有效对象或字符串

i use below code for remove one record from roles table:

if ( $role = Role::find($id)) {
    $role->delete();

    return response()->json(['status' => 'success', 'message' => 'operation was successful.']);
}

but, an error happen and the message is:

Class name must be a valid object or a string

i google it!, for some answer i had to say config/entrust.php file exist.

delete() method dos not work on Role Model, in this situation for delete one record or one role after find for exp Role::whereId($id)->delete(); work for me and my problem solved for no.

Add this method in Role model:

use Illuminate\Support\Facades\Config;

public function users()
{
    return $this->belongsToMany(
        Config::get('auth.providers.users.model'),
        Config::get('entrust.role_user_table'),
        Config::get('entrust.role_foreign_key'),
        Config::get('entrust.user_foreign_key')
    );
}