Laravel: Eloquent relationships with *where* on parent table instead of *find* - php

Question

I have a table posts and posts_contents.
And I want to get a content from one post only if that post has display = 1.
(I need two separate tables because of language support)
posts:
id user_id display
1 2 0
2 2 1
3 2 0
4 2 1
posts_contents
id post_id lang_id name description
1 1 1 Hello World
2 2 1 Here Is What I wanna show!
3 3 1 Don't Show the others
4 4 1 Hey Display that one too
So in laravel I use eloquent relationships, but I just don't understand how to use it in that particular case. In the documentation I found only cases such as:
$p = App\Posts::find(1)->contents;
Which works great, however what I want is something like this:
$p = App\Posts::where('display',1)->contents;
But it doesn't work... So question is: what is the right way to do so?
Any help is appreciated, Thanks!
Update
I need to get multiple posts at once, not just one.

Answer 1

You want to use find() method like this:
$post = App\Posts::where('display', 1)->find($postId)->contents;
Then in a view for one-to-one relationship:
{{ $post->description }}
For one-to-many:
#foreach ($post->contents as $content)
{{ $content->description }}
#endforeach
If you want to load multiple posts with contents only for one language, use filtering by a language. Use with() to eager load contents:
$posts = App\Posts::where('display', 1)
->with(['contents' => function($q) use($langId) {
$q->where('lang_id', $langId);
}])
->get();
Then in a view for one-to-one:
#foreach ($posts as $post)
{{ $post->contents->description }}
#endforeach
For one-to-many:
#foreach ($posts as $post)
#foreach ($post->contents as $content)
{{ $content->description }}
#endforeach
#endforeach
You can read about the difference between find() and get() methods here.

Answer 2

App\Posts::where will return a collection. So if you only want 1 result you should use App\Posts::where('display',1)->first()->contents

Answer 3

You need to call the first method before you call any relationship:
$p = App\Posts::where('display', 1)->first()->contents;
Or, if you want to fetch a collection of posts, you can:
$posts = App\Posts::where('display', 1)->get();
$posts->each(function ($post) {
$post->contents;
});
Otherwise, you will just have a Query Builder object, without the actual results you want.