如何在 Laravel 中获取外键的值

Question

我对 Laravel 模型关系有疑问。我需要让用户创建新卡车。但是，我需要将制造商的字段存储为 ID，而不是标题。所以我决定制作两个具有一对多关系的表（制造商和卡车）（制造商有多辆卡车，而一辆卡车有一个制造商）。

这是迁移文件。制造商表：

public function up()

{

    Schema::create('manufacturers', function (Blueprint $table) {

        $table->bigIncrements('id');

        $table->string('manufacturer');

        $table->timestamps();

    });

}

卡车表：

public function up()

{

    Schema::create('trucks', function (Blueprint $table) {

        $table->bigIncrements('id');

        $table->unsignedBigInteger('make_id');

        $table->unsignedInteger('year');

        $table->string('owner');

        $table->unsignedInteger('owner_number')->nullable();

        $table->text('comments')->nullable();

        $table->foreign('make_id')->references('id')->on('manufacturers');

        $table->timestamps();

    });

}

Manufacturer.php模型：

namespace App;

use Illuminate\Database\Eloquent\Model;

class Manufacturer extends Model

{

/**

 * @var string

 */

protected $table = 'manufacturers';

/**

 * @var array

 */

protected $fillable = [

    'manufacturer', 

];

public function trucks(){

    return $this->hasMany(Truck::class);

}

}

Truck.php 模型：

namespace App;

use Illuminate\Database\Eloquent\Model;

 class Truck extends Model

 {

 /**

 * @var string

 */

protected $table = 'trucks';

/**

 * @var array

 */

protected $fillable = [

    'make_id', 'year', 'owner', 'owner_number', 'comments',

];

public function manufacturer(){

    return $this->belongsTo(Manufacturer::class);

}

}

控制器文件：

public function index()

{

    $trucks = Truck::all();

    return view('trucks.index')->with('trucks', $trucks);

}

索引.blade.php

@foreach($trucks as $truck)

            <tbody>

            <tr>

                <td>{{$truck->make_id}}</td> //I need this one to show manufacturers title

                <td>{{$truck->year}}</td>

                <td>{{$truck->owner}}</td>

                <td>{{$truck->owner_number}}</td>

                <td>{{$truck->comments}}</td>

            </tr>

            </tbody>

            @endforeach

此视图现在显示 id。我需要做什么来显示制造商标题（manufacturers.manufacturer）而不是 id？谢谢大家！

Answer 1

卡车表中制造商的外键不是 manufacturer_id。在这种情况下，您需要在模型中声明它：return&nbsp;$this->belongsTo(Manufacturer::class,&nbsp;'make_id'&nbsp;)和&nbsp;return&nbsp;$this->hasMany(Truck::class,&nbsp;'make_id'&nbsp;)