在 Laravel 5.2 中使用 eloquent 而不是查询

Question

I made a query, but I'm not satisfied, because I wanted to do it with Eloquent!

Here is the query:

Tournament::leftJoin('category_tournament', 'category_tournament.tournament_id', '=', 'tournament.id')
        ->leftJoin('category_tournament_user', 'category_tournament_user.category_tournament_id', '=', 'category_tournament.id' )
        ->where('category_tournament_user.user_id', '=',$this->id )
        ->select('tournament.*')
        ->distinct()
        ->get();

Migrations:

Schema::create('tournaments', function(Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->timestamps();
});

Schema::create('categories', function(Blueprint $table) {
    $table->increments('id');
    $table->string('name');
    $table->timestamps();
});

Schema::create('category_tournament', function(Blueprint $table) {
    $table->increments('id');
    $table->integer('category_id');
    $table->integer('tournament_id');
    $table->timestamps();

    $table->foreign('tournament_id')
            ->references('id')
            ->on('tournament')
            ->onDelete('cascade');

        $table->foreign('category_id')
            ->references('id')
            ->on('category')
            ->onDelete('cascade');
});

Schema::create('category_tournament_user', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('category_tournament_id')->unsigned()->index();
        $table->foreign('category_tournament_id')
            ->references('id')
            ->on('category_tournament')
            ->onDelete('cascade');


        $table->integer('user_id')->unsigned()->index();
        $table->foreign('user_id')
            ->references('id')
            ->on('users')
            ->onDelete('cascade');

        $table->unique(array('category_tournament_id', 'user_id'));

        $table->boolean('confirmed');

        $table->timestamps();
        $table->softDeletes();
        $table->engine = 'InnoDB';


    });

Models

class Tournament extends Model
{
    public function categories()
    {
        return $this->belongsToMany(Category::class);
    }

    public function categoryTournaments()
    {
        return $this->hasMany(CategoryTournament::class);
    }
}

class Category extends Model
{
    public function tournaments()
    {
        return $this->belongsToMany(Tournament::class);
    }

    public function categoryTournament()
    {
        return $this->hasMany(CategoryTournament::class);
    }
}

class CategoryTournament extends Model
{
    protected $table = 'category_tournament';

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

    public function tournament()
    {
        return $this->belongsTo(Tournament::class);
    }

    public function users()
    {
        return $this->belongsToMany(User::class, 'category_tournament_user');
    }
}

class User extends Authenticatable
{
    public function categoryTournaments()
    {
        return $this->belongsToMany(CategoryTournament::class, 'category_tournament_user');
    }
}

The query works, I just want to know how should I do it with Eloquent because I was not able to do it by myself :(

Any idea how to do it???

Answer 1

First of all you have to add foreign keys to your migrations Table + it's useful to make them unsigned since you will probably never have any negative ids:

$table->integer('tournament_id')->unsigned();
$table->foreign('tournament_id')->references('id')->on('tournaments');

Since you already have the relations for your Model you should be able to use eloquent to get the contents.

You can stick to this page for further information on Eloquent: https://laravel.com/docs/5.0/eloquent

Should be something like this:

$tournaments = Tournament::with('category_tournament')
   ->with('category_tournament_user')    
   ->where('category_tournament_user.user_id', '=',$this->id ) 
   ->distinct()
   ->get();

You can use the contents of $tournaments afterwards:

$tournaments->category_tournament->name;

Hope I didn't miss any crucial step, but I think it should be working by doing these changes.

Edit:

https://laravel.com/docs/5.1/eloquent-relationships#eager-loading

When accessing Eloquent relationships as properties, the relationship data is "lazy loaded". This means the relationship data is not actually loaded until you first access the property. However, Eloquent can "eager load" relationships at the time you query the parent model. Eager loading alleviates the N + 1 query problem. To illustrate the N + 1 query problem, consider a Book model that is related to Author: