Question

namespace App;

use App\Model\Service\Area;
use App\Model\Bid\Service;
use Illuminate\Database\Eloquent\Model;

class Bid extends Model
{
    protected $table = "bid";

    protected $primaryKey = 'bid_id';

    protected $guarded = [];

    protected $with = ['services'];

    public function services() {
        return $this->hasMany(Service::class, 'bid_id');
    }

    public function area() {
        return $this->belongsTo(Area::class, 'area_id', 'area_id');
    }
}

namespace App\Model\Service;

use Illuminate\Database\Eloquent\Model;

class Area extends Model
{
    protected $table = "location_area";

    protected $primaryKey = 'area_id';

    protected $guarded = [];

    public function city()
    {
        return $this->belongsTo(City::class, 'city_id');
    }
}

Area table Migration and data

Bid table Migration and data

当我尝试访问时

Bid::with('area')->find(BID_ID);

返回Null 查询触发错误：

"select * from `location_area` where `location_area`.`area_id` in (0)"

但是，如果我这样做：

$bid = Bid::find(BID_ID);
dd($bid->area);

它返回Area表值。怎么了？请帮我。一世长期有这个问题。预先谢谢你：）

Answer 1

必须在 MID模型

中将您声明为方法

    public function area()
        {
            return $this->belongsTo(Area::class, 'bid');
        }

像这样的东西之后，您访问with()

中的区域

Bid::with('area')->find(BID_ID);

Answer 2

在您的Bid模型中更改此功能：

 public function area() {
        return $this->belongsTo(Area::class, 'area_id');
    }

Laravel雄辩with（）返回null

2 个答案: