在 Laravel Eloquent 中使用两个一对多关系进行约束

Question

我想使用 Laravel Eloquent 约束使用两个一对多的关系；当添加第二个约束作为方法时，错误表明查询正在与我实际需要的相反运行，我对 Laravel 的经验还不够，还不知道为什么会发生这种情况。

 class YeargroupController extends Controller
    {
        public function index($id)     
        {      
            $yeargroups = Yeargroup::get();
            $objectives = Yeargroup::find(1)->objectives->where('subject_id',$id);
            
            return view('admin.yeargroups.index',[
                'yeargroups' => Yeargroup::with('objectives.subjects')->get(),
            ],compact('objectives','yeargroups'));
        }
    }

模型

class Objective extends Model
{
    
     public function subjects() {
        return $this->hasOne('App\Models\Subject');
    }
     
    public function yeargroups()
    {
        return $this->hasOne('App\Models\Yeargroup');
    }
}

class Subject extends Model
{

    public function objectives() {
        return $this->hasMany('App\Models\Objective');
    }
}

class Yeargroup extends Model
{
    
    public function objectives()
    {
        return $this->hasMany('App\Models\Objective');
    }
}

错误

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'subjects.objective_id' in 'where clause' (SQL: select * from `subjects` where `subjects`.`objective_id` in (1, 2) and `subjects`.`deleted_at` is null)

Answer 1

像这样更改您的目标模型：

class Objective extends Model
{
    
     public function subjects() {
        return $this->belongsTo('App\Models\Subject');
    }
     
    public function yeargroups()
    {
        return $this->belongsTo('App\Models\Yeargroup');
    }
}

在此处阅读更多信息：https://laravel.com/docs/8.x/eloquent-relationships#one-to-many-inverse