如何从Laravel中的远距离关系中挑选田野

Question

I have a many to one relationship for getting each product its images, every product should have a lot of images to view it to user. so I tried to get stocks with images when I do

 public function getImages() {
        $stocks = Stocks::with('images', 'tags')->get();
        return $stocks;
    }

it returns this

[
   {
       "id": 7,
       "name": "1",
       "descriptions": "1",
       "price": 1,
       "discount": 1,
       "category": "new",
       "quantity": 1,
       "brand": "1",
       "created_at": "2019-08-04 09:07:25",
       "updated_at": "2019-08-04 09:07:25",
       "images": [
           {
               "id": 6,
               "url": "1564909645iKiw2LkoEcQIIhB4MTZJTUfwTREleWH4wEuvmRPd.png",
               "created_at": "2019-08-04 09:07:25",
               "updated_at": "2019-08-04 09:07:25",
               "pivot": {
                   "stocks_id": 7,
                   "images_id": 6
               }
           },
           {
               "id": 7,
               "url": "1564909645OVxnM0qmoQayZrP7wq82pTmSj1AwQc9gioyC5L7h.png",
               "created_at": "2019-08-04 09:07:25",
               "updated_at": "2019-08-04 09:07:25",
               "pivot": {
                   "stocks_id": 7,
                   "images_id": 7
               }
           }
       ],
       "tags": [
           {
               "id": 1,
               "tag": "عطور",
               "created_at": "2019-08-03 17:45:52",
               "updated_at": "2019-08-03 17:45:52",
               "pivot": {
                   "stocks_id": 7,
                   "tag_id": 1
               }
           }
       ]
   }
]

but I want "images" to have only urls as strings like:

"images":[1.png,2.png,3.png .....]

what should I do?

my relation

public function images()
    {
        return $this->belongsToMany('App\Images', 'stock_images');
    }

Answer 1

You can pass a closure when eager loading relationships with the function with() .

In that closure you can use the select function to filter columns.

$stocks = Stock::with('tags')
              ->with(['images' => function ($query) {
                  $query->select(['id', 'url']);
              }])
              ->get();

UPDATE

If you want only the values without keys, you cannot use this approach. You have to do it after fetching the data from the database. like this..

$stocks = Stock::with('images', 'tags')->get()->map(function ($stock) {
    $stock->images = $stock->images->map->url->values();

    $stock->unsetRelation('images');

    return $stock;
});

Answer 2

You need to make your query like this:

$stocks = Stock::with(['tags','images' => function ($query) {
              $query->get()->pluck('url');
          }])->get();

Answer 3

but I want "images" to have only urls as strings like:

 "images":[1.png,2.png,3.png .....] 

what should I do?

The quickest solution would be to add the $visible property to your App\\Images model, like so:

public $visible = ['url'];

This will remove all the fields from the json, including the pivot field, except for those defined in the visible property. This solution works fine but it still selects all columns from the images table, if you want it to select only the minimum required fields (so you improve performance) for the relation, you can do:

$stocks = Stocks::with('images:url', 'tags')->get(); // this is a shortcut for selecting only url

Please, be aware that the solution above works fine for ManyToMany (N:N) relationships. However, for a hasMany (1:N), you'd have to select the primary key and all related foreign keys as well.

Hope it helps.

References:

Eloquent: Relationships#Eager-Loading

UPDATE

It worked but how can I remove the key url: and store only values 1,2,3

->pluck() is the collection function to do that, however, you can't easily pluck fields from a distant relationship without discarding the rest, but this macro will do the trick.

->pluckDistant()

In your AppServiceProvider , under the boot method, add this macro function:

public function boot()
{
    /**
     * Shortcut to pluck a field in a relationship.
     *
     * @param string $relationship The relationship name
     * @param string|array $value
     * @param string|null $key
     */
    collect()->macro('pluckDistant', function($relationship, $value, $key = null) {
        return $this->map(function($item) use($relationship, $value, $key) {
            $relation = $item->getRelation($relationship);

            if (get_class($relation) == \Illuminate\Support\Collection::class ||
                get_class($relation) == \Illuminate\Database\Eloquent\Collection::class) {
                $item->setRelation($relationship, $relation->pluck($value, $key));
            }

            return $item;
        });
    });
}

And then, you do this:

$stocks = Stocks::with('images:url', 'tags')->get()->pluckDistant('images', 'url');