one to many relation is not working

Question

I have a question about one to many relation of laravel.

I am trying to make programs based on this page. https://manablog.org/laravel_bulletin_board/

My programs are here.

class PostsController extends Controller
{
  public function index()
  {
      \DB::enableQueryLog();
      $comments = Post::find(9)->comments;
      $query = \DB::getQueryLog();

      Log::debug($query);

      $posts = Post::all();
      $query = \DB::getQueryLog();
      Log::debug($query);

      return view('bbc.index')->with('posts', $posts);
  }
}
class Post extends Model {

    protected $table = 'posts';
    protected $connection = 'mysql';

    public function comments(){
        return $this->hasMany('App\Comment','post_id', 'id');
    }


}
class Comment extends Model{

    protected $table = 'comments';
    protected $connection = 'mysql';

    public function post() {
        return $this->belongsTo('App\Post');
    }

}

tables are here.

mysql> desc comments;
+------------+------------------+------+-----+---------+----------------+
| Field      | Type             | Null | Key | Default | Extra          |
+------------+------------------+------+-----+---------+----------------+
| Id         | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| post_id    | int(10) unsigned | NO   | MUL | NULL    |                |
| name       | varchar(50)      | NO   |     | NULL    |                |
| content    | varchar(300)     | NO   |     | NULL    |                |
| created_at | timestamp        | YES  |     | NULL    |                |
| updated_at | timestamp        | YES  |     | NULL    |                |
+------------+------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)

mysql> desc posts;
+------------+------------------+------+-----+---------+----------------+
| Field      | Type             | Null | Key | Default | Extra          |
+------------+------------------+------+-----+---------+----------------+
| Id         | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| name       | varchar(50)      | NO   |     | NULL    |                |
| title      | varchar(50)      | NO   |     | NULL    |                |
| content    | varchar(300)     | NO   |     | NULL    |                |
| created_at | timestamp        | YES  |     | NULL    |                |
| updated_at | timestamp        | YES  |     | NULL    |                |
+------------+------------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)

But my program did not work what i expected. then i checked the log. Logs are here.

[2017-08-31 18:25:47] local.DEBUG: array (
  0 =>
  array (
    'query' => 'select * from `posts` where `posts`.`id` = ? limit 1',
    'bindings' =>
    array (
      0 => 9,
    ),
    'time' => 4.5099999999999998,
  ),
  1 =>
  array (
    'query' => 'select * from `comments` where `comments`.`post_id` is null and `comments`.`post_id` is not null',
    'bindings' =>
    array (
    ),
    'time' => 0.53000000000000003,
  ),
)

there are no relation. And i can't understand why 'select * from comments where comments.post_id is null and comments.post_id is not null' is here. what is this problem?

Answer 1

I would imagine the issue is because your id column is Id and not id.

MySQL itself is case insensitive, however, PHP is not.

You can either:

• change Id to id in your database (and migrations files if applicable)

or

• add the following to your models:

   protected $primaryKey = 'Id'; 
  

and either change your relationship to:

    public function comments() {
        return $this->hasMany('App\Comment');
    }
    //or
    public function comments() {
        return $this->hasMany('App\Comment', 'post_id', 'Id');
    }