在laravel中与模型工厂建立多对多关系-列不能为空错误 [英] Seeding many-to-many relationship with model factory in laravel - column cannot be null error

问题描述

鉴于我有以下表格:

• 用户
• 问题
• 标签
• question_tag my pivot table with two fields: question_id & tag_id

• users
• questions
• tags
• question_tag my pivot table with two fields: question_id & tag_id

这些是我的模型关系:

用户

public function questions()
{
    return $this->hasMany(Question::class);
}

问题

public function user()
{
    return $this->belongsTo(User::class);
}

public function tags()
{
    return $this->belongsToMany(Tag::class);
}

标记

public function questions()
{
    return $this->belongsToMany(Question::class);
}

我已经为每种模型正确设置了数据库模型工厂.

I have setup the database model factory correctly for each models.

使用播种机，这是我要实现的目标:

With my seeder, here's what I am trying to achieve:

1. 种子10个虚拟用户
2. 为每个虚拟用户播种10个虚拟问题
3. 对于每个虚拟问题，将其与最多5个随机标签相关联

为了实现上述三个目标，我编写了以下数据库种子器:

To achieve the above three goals, I wrote the following database seeder:

// Seed dummy users
factory(App\User::class, 10)->create()->each(function($user)
{
    // With dummy questions
    $user->questions()->saveMany(factory(App\Question::class, 10)->make()->each(function($question)
    {
        // With dummy tags
        $question->tags()->sync(factory(App\Tag::class, 5)->make());
    }));
});

运行时，出现以下错误:

When this runs, I am getting the following error:

[Illuminate \ Database \ QueryException] SQLSTATE [23000]:完整性 违反约束:1048列'question_id'不能为null(SQL:i 插入question_tag(question_id，tag_id)值(，1))

[Illuminate\Database\QueryException] SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'question_id' cannot be null (SQL: i nsert into question_tag (question_id, tag_id) values (, 1))

[PDOException] SQLSTATE [23000]:违反完整性约束: 1048'question_id'列不能为空

[PDOException] SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'question_id' cannot be null

在通过数据库模型工厂创建记录的同时，如何为数据透视表添加种子?

How do you seed a pivot table, whilst creating records via the database model factory?

这个问题与我问的另一个问题相关-但是现在我遇到了另一个错误.

This question is related to another question I asked - but now I am getting a different error.

推荐答案

我已经解决了这个问题:

I've solved it like this:

<?php

use Illuminate\Database\Seeder;

class DummyDataSeeder extends Seeder
{
    public function run()
    {
        // Seed dummy tags
        factory(App\Tag::class, 10)->create();
        $tagIds = DB::table('tags')->pluck('id')->toArray();

        // Seed dummy users
        factory(App\User::class, 10)->create()->each(function($user) use($tagIds)
        {
            // With dummy questions
            $user->questions()->saveMany(factory(App\Question::class, 3)
            ->create(['user_id' => $user->id])->each(function($question) use($tagIds)
            {
                // With dummy tags
                $question->tags()->sync(array_random($tagIds, mt_rand(1, 5)));
            }));
        });
    }
}

也许有更好的方法可以做到这一点；但这对我有用.

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