Trying to Create Fake Posts on Laravel but meeting with QueryException with message 'SQLSTATE[23000]

Question

Trying to create Fake Posts by using tinker but met with the error code bellow

Illuminate\Database\QueryException with message 'SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails ( posty . posts , CONSTRAINT posts_user_id_foreign FOREIGN KEY ( user_id ) REFERENCES users ( id ) ON DELETE CASCADE) (SQL: insert into posts ( body , user_id , updated_at , created_at ) values (Velit deserunt tempore vitae et et aliquid explicabo autem occaecati dolores veritatis accusamus cum natus sint eius laudantium mollitia maxime dolorem eius enim., 2, 2021-04-13 08:42:17, 2021-04-13 08:42:17))'

Below are my codes

PostFactory.php

<?php

namespace Database\Factories;

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

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()
    {
        return [
            'body' => $this->faker->sentence(20),
                ];
    }
}

PostController.php

<?php

namespace App\Http\Controllers;

use App\Models\Post;
use Illuminate\Http\Request;

class PostController extends Controller
{
    public function index(){
        // $posts= Post::get(); //Collect all...
        $posts= Post::paginate(20); //How many you want per page...

        return view('posts.index', [
            'posts' => $posts
        ]);
    }

    public function store(Request $request)
    {
        //dd('ok');
         $this->validate($request, [
             'body' => 'required',
         ]);

        Post::create([
            'user_id' => auth()->id(),
            'body' => $request->body,

        ]);



        return back();
    }
}

Post.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    use HasFactory;

    protected $fillable= [
        'body',
        'user_id',
    ];

   /**
     * Get the user that owns the Post
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

Answer 1

Cannot add or update a child row: a foreign key constraint fails essentially means that, you are trying to add a row to your posts table for which no matching row (user_id) is present in user table.

Answer 2

Try to change relationship function in model Post with this:

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

Without this change you are trying to 'connect' Post.id (instead of user_id) with User.id, and Post.id doesn't seem to exist, at least by wath I see from the log.

Answer 3

1. The user_id had errors while I was trying to create the fake posts using tkinter because I was assigning to a different user_id.

2. As @AliAli has said, I had to remove the username from nullable.