Laravel seed的问题

Question

我是Laravel初学者，我试图建立一个简单的数据库。这个问题是关于外键的一个问题。我看了文档，但我没有找到任何解决方案。

这是错误: SQLSTATE23000:完整性约束冲突: 1452无法添加或更新子行:外键约束失败(vlogit。posts，constraint posts_user_id_foreign外键(user_id)引用users (id) ON DELETE CASCADE ON UPDATE CASCADE) (SQL: insert insert posts (user_id，category_id，name，slug，excerpt，body，file，status，updated_at，created_at)值(28，18，Voluptas qui - ut.，voluptas-qui-ut，voluptas-qui-ut，我买了一辆大车。最低限度的指控是偶然发生的。最好的解决办法是。他说：“我不知道你的工作是什么，我的工作是什么？”劳力等人指控他的身份。结论:我的意思是我的收入是最好的。这是一种新的方法。最大的问题就是。莫列蒂亚·伊莱姆指责我坐在非易懂的地方。你逃亡的后果是什么。天鹅绒和羊毛绒。没有人知道我的工作是什么。这是一种伪装的说法。Ea sit ad officiis quam，https://via.placeholder.com/1200x400.png/0066cc?text=voluptas，发布，2020-11-21 23:46:59,2020-11-21 23:46:59)

数据库是关于一个简单的博客，与用户，类别，帖子和标签列。数据库可以正确地处理帖子、类别和用户，但不能处理post_tags。我认为这个错误是这样产生的：

The migration:post_tag_table

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreatePostTagTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('post_tag', function (Blueprint $table) {
            $table->increments('id');

            $table->integer('post_id')->unsigned();
            $table->integer('tag_id')->unsigned();
            $table->timestamps();
            
            //Relaciones
            $table->foreign('post_id')->references('id')->on('posts')
                ->onDelete('cascade')
                ->onUpdate('cascade');

            $table->foreign('tag_id')->references('id')->on('tags')
                ->onDelete('cascade')
                ->onUpdate('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('post_tag');
    }
}

PostFactory.php

<?php

namespace Database\Factories;

use App\Models\Post;
use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;

class PostFactory extends Factory
{
    /**
     * The name of the factory's corresponding model.
     *
     * @var string
     */
    protected $model = Post::class;

    /**
     * Define the model's default state.
     *
     * @return array
     */
    public function definition()
    {
        
        $title = $this->faker->sentence(4);
        return [
            
            'user_id'       => rand(1,30),
            'category_id'   => rand(1,20),
            'name'          => $title,
            'slug'          => Str::slug($title),
            'excerpt' => $this->faker->text(200),
            'body' => $this->faker->text(500),
            'file' => $this->faker->imageUrl($width = 1200, $height = 400),
            'status' =>$this->faker->randomElement(['DRAFT', 'PUBLISHED']),
        ];
    }
}

TagFactory.php

<?php

namespace Database\Factories;

use App\Models\Tag;
use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;

class TagFactory extends Factory
{
    /**
     * The name of the factory's corresponding model.
     *
     * @var string
     */
    protected $model = Tag::class;

    /**
     * Define the model's default state.
     *
     * @return array
     */
    public function definition()
    {
        $title = $this->faker->sentence(4);
        return [
            
        'name' => $title,
        'slug' => Str::slug($title),
            
        ];
    }
}

PostTableSeeder.php

<?php

namespace Database\Seeders;

use Illuminate\Database\Seeder;

class PostsTableSeeder extends Seeder
{
    /**
     * Run the database seeds.
     *
     * @return void
     */
    public function run()
    {
        
        //      
        \App\Models\Post::factory(300)->create()->each(function(\App\Models\Post $post) {
            $post->tags()->attach([
                rand(1,5), 
                rand(6,14), 
                rand(15,20)
            ]);
            
        });
    }
}

Answer 1

正如@lagbox所指出的，users表中应该有30条记录，ids在1-30之间。

然而，更合适的方式来定义后工厂-拉威尔方式是通过工厂'user_id' => \App\Models\User::factory()利用关系

<?php

namespace Database\Factories;

use App\Models\Post;
use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;

class PostFactory extends Factory
{
    /**
     * The name of the factory's corresponding model.
     *
     * @var string
     */
    protected $model = Post::class;

    /**
     * Define the model's default state.
     *
     * @return array
     */
    public function definition()
    {
        
        $title = $this->faker->sentence(4);
        return [
            
            'user_id'       => \App\Models\User::factory(),
            'category_id'   => rand(1,20),
            'name'          => $title,
            'slug'          => Str::slug($title),
            'excerpt' => $this->faker->text(200),
            'body' => $this->faker->text(500),
            'file' => $this->faker->imageUrl($width = 1200, $height = 400),
            'status' =>$this->faker->randomElement(['DRAFT', 'PUBLISHED']),
        ];
    }
}

另一件需要记住的事情是迁移的顺序。

Answer 2

解决了。这是通用种子文件中的一个问题。

DatabaseSeeder.php

$this->call(UsersTableSeeder::class);
$this->call(CategoriesTableSeeder::class);
$this->call(TagsTableSeeder::class);
$this->call(PostsTableSeeder::class);

现在可以正常工作了。

CategoriesTableSeeder.php

 public function definition()
    {
        
        $title = $this->faker->sentence(4);
        return [
            
        'name' => $title,
        'slug' => Str::slug($title),
        'body' => $this->faker->text(500),
            
  
        ];
    }

PostTableSeeder.php

public function definition()
{
    
    $title = $this->faker->sentence(4);
    return [
        
        'user_id'       => rand(1,30),
        'category_id'   => rand(1,30),
        'name'          => $title,
        'slug'          => Str::slug($title),
        'excerpt' => $this->faker->text(200),
        'body' => $this->faker->text(500),
        'file' => $this->faker->imageUrl($width = 1200, $height = 400),
        'status' =>$this->faker->randomElement(['DRAFT', 'PUBLISHED']),
    ];
}

TagTableSeeder.php

public function definition()
{
    $title = $this->faker->unique()->word(4);
    return [
        
    'name' => $title,
    'slug' => Str::slug($title),
        
    ];
}

我分享这些代码是为了帮助其他初学者。