Laravel中表之间的雄辩关系

Question

I have three tables:

1. collections which has id , name
2. genre_collection which has id , genre_id , collection_id
3. genres which has id , name

I want to retrieve data from collections with generes.

Collections Model

class Collections extends Model{
    public function genres(){
        return $this->hasMany('App\Models\GenreCollectionRelationships', 'genre_id' , 'id');
    }
}

generic_collection

class GenreCollectionRelationships extends Model{
    public function genre(){
        return $this->hasOne('App\Models\Genres', 'id', 'genre_id');
    }
}

Search Controller

class SearchController extends Controller{
    $collection->genres;
    foreach($collection->genres as $item){
        $item->genre;
    }
}

This code is working fine. And the output is

Actual

"genres": [{
    "id": 1,
    "genre_id": 1,
    "collection_id": 1,
    "created_at": "2019-02-07 17:13:36",
    "updated_at": "2019-02-07 17:13:36",
    "genre": {
        "name": "Action",
        "meta": null
    }
}]

Is there any way i could directly get the output as shown below

Expected

"genres": [ {
    "name": "Action",
    "meta": null
}]

I tried hasManyThrough, belongsToMany but nothing worked out.

Note. I am on laravel 5.7

Thanks in advance.

Answer 1

You could build your own query to achieve what you are looking for. Try this:

$collection = Collection
        ::join('genres', 'genre.id', '=', 'collections.genre_id')
        ->select('collections.*', 'genres.name','genre.meta')
        ->get();

Answer 2

I find your code a bit hard to follow... Let me try and see if I understood it correctly...

You basically have two models:

• Model Collection saved in table collections
• Model Genre saved in table genres

Since you have a many to many relationship between them, you need a third table to link the both of them together.

By naming convention, Laravel expects you to name it based on the two models, ordered alphabetically. So to create a link between collections and genres, you would need to create a table collection_genre which has a collection_id as a reference to the collections table, and likewise a genre_id to identify the linked genre.

You can then define your relationships as follows:

class Collection extends Model {
    public function genres() {
       $this->belongsToMany(\App\Models\Genre::class);
    }
}

and

class Genre extends Model {
    public function collections() {
       $this->belongsToMany(\App\Models\Collection::class);
    }
}

Now, I'm not sure what your controller looks like as the question has some invalid code to it, but I suspect you want to search the genres for a given collection.

Your code could like like this:

Class CollectionController extends Controller {

    function getGenres(Collection $collection) {
        return $collection->genres;
    }
}

This would return the genres for the given collection. If you want to format this, you could create an Eloquent Resource for this:

Class CollectionResource extends Resource {
    public function toArray() {
        return [
           'name' => $this->name,
           'meta' => $this->meta
        ];
    }
}

In your controller you can then do:

Class CollectionController extends Controller {

    function getGenres(Collection $collection) {
        return CollectionResource::collection($collection->genres);
    }
}

Answer 3

in your collection model

class Collections extends Model
{
    protected $table='collections';
    public $primaryKey='id';
    protected $fillable = ['name'];

    public function genres()
     {
            return $this->belongsToMany('App\Model\Genres','genre_collection','collection_id','genre_id')->withTimestamps();
     }

}

in your genres model

class Genre extends Model {

  protected $table='genres';
  public $primaryKey='id';
  protected $fillable = ['name'];


    public function collections()
    {
        return $this->belongsToMany('App\Model\Collections','genre_collection','genre_id','collection_id')->get();
    }

}

Answer 4

You are creating many to many relationship between collections and genre using genre_collection pivot table. In that case, belongsToMany is appropriate. And you don't need any model for genre_collection table.

Collections model

class Collections extends Model
{
    public function genres(){
        return $this->belongsToMany('App\Models\Genres', 'genre_collection', 'genre_id', 'collection_id');
    }
}

Genres model

class Genres extends Model
{

    public function collections(){
        return $this->belongsToMany('App\Models\Collections', 'genre_collection', 'collection_id', 'genre_id');
    }
}

SearchController

class SearchController extends Controller
{
    foreach($collection->genres as $item){
        $item->genre; // get genre info
    }
}

Answer 5

I'm assuming that you want to access Generic directly from collection . If this is the case you can define a many-to-many relationship in collection model directly to generic model to access it . Please refer this : https://laravel.com/docs/5.7/eloquent-relationships#many-to-many . Sorry if I'm wrong