Laravel | 雄辩地填充外国数据

Question

I have a database which is set out with a news and a news categories tables.

I have news which has a category 1 which links to a foreign key of the categories table where the category value equals the id in the categories table.

I'm trying to make a controller that gets the category name rather than the category ID when returning the results as a JSON response.

So far I have this inside of a model:

public function category()
{
    return $this->belongsTo(NewsCategories::class);
}

And then I'm doing this inside of a controller:

public function index()
{
    $news = new News();
    $news = $news->category()->get();

    return response()->json(['data' => $news], 200);
}

But the JSON response that gets returned is empty. I have googled some things but haven't really found anything useful regarding getting the foreign field which is title within the categories table.

This is the response that I get

{
  data: [ ]
}

Answer 1

The first issue is that you're under the impression that your new News instance has linked categories:

$news = new News();

This will yield just an empty model instance; it has no database representation yet. Try fetching categories through a populated model instance:

$news = News::first();

// Or:
$news = News::find(1);

and retry the JSON response.

Second issue is that by calling $news->category()->get() you're actually querying the relation. If you only need to access the title, try $news->category->title which will load the associated category record and access the title field for you.

---

Regarding your comment, read on eager/lazy loading.