[FIXED] Fetch specific fields on a hasMany relation

Issue

I have a hasMany relation function like this:

public function articles()
{
    return $this->hasMany('App\Article');
}

And use it like this:

$data = \App\User::with('articles')->get();

I don't have any problems with it, since it's returning the expected data. Something like this:

{
"id": 1,
"name": "Jhon",
"lastname": "Doe",
"articles": [
    {
        "id": 1,
        "title": "Article 1",
        "status": "published",
        "published_at": "2015-04-30"
    },
    {
        "id": 2,
        "title": "Article 2",
        "status": "draft",
        "published_at": null
    }
 ]
}

What I am trying to achieve but I still can't it's to fetch just a subset of the relation's fields to obtain this:

{
"id": 1,
"name": "Jhon",
"lastname": "Doe",
"articles": [
    {
        "id": 1,
        "title": "Article 1"
    },
    {
        "id": 2,
        "title": "Article 2"
    }
  ]
}

My intention is to find a way to specify the subset of fields in the Model's function instead of iterating the returning collection and unset the unwanted fields.

Is this possible?

Solution

Yes, it's possible. You've got a couple options.

*NB: For options 1 and 2 below, the foreign key (user_id) must be selected so that Laravel knows how to link the models together when building the relationships.

1. Modify the relationship query when using it. The with() method can accept an array of key/value pairs where the key is the name of the relationship and the value is a Closure that modifies the relationship query.

    $data = \App\User::with(['articles' => function($query) {
        // user_id is required here*
        $query->select(['id', 'title', 'user_id']);
    }])->get();
   

2. Create a new relationship that contains the fields you want.

    public function articleTitles() {
        // user_id is required here*
        return $this->hasMany('App\Article')->select(['id', 'title', 'user_id']);
    }
   
    $data = \App\User::with('articleTitles')->get();
   

3. If you're only concerned about the array/json output, you can modify the App\Article model to only display the id and title when converted to an array.

    class Article extends Model {
        protected $visible = ['id', 'title'];
    }
   

What you choose depends on what you need.

Answered By - patricus