Foreign Key not working in Laravel

Question

I am creating cms app.

There are two tables - users and posts. Users table have an id of each user. On the other hand, Posts Table has user id which references to the id of users table.

However, while saving the post, I get an error that Field 'user_id' doesn't have a default value. Why is this? Please help me.

Posts Table:

<?php

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

class CreatePostsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->increments('id');
            $table->integer('user_id');
            $table->foreign('user_id')->references('id')->on('users');
            $table->string('title');
            $table->longText('description');
            $table->timestamps();
        });
    }

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

DashboardController

<?php

namespace App\Http\Controllers\Dashboard;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use App\Post;

class DashboardController extends Controller
{
    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        return view('dashboard.index');
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        return view('dashboard.create');
    }

    /**
     * Store a newly created resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @return \Illuminate\Http\Response
     */
    public function store(Request $request)
    {
        $post = new Post();
        $post->title = $request->title;
        $post->description = $request->description;
        $post->save();

        return redirect()->intended('dashboard');
    }

    /**
     * Display the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function show($id)
    {
        //
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function edit($id)
    {
        //
    }

    /**
     * Update the specified resource in storage.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, $id)
    {
        //
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param  int  $id
     * @return \Illuminate\Http\Response
     */
    public function destroy($id)
    {
        //
    }
}

Post model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    //
}

User model:

<?php

namespace App;

use Illuminate\Notifications\Notifiable;
use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable
{
    use Notifiable;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'fname', 'lname', 'email', 'password'
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [
        'password', 'remember_token',
    ];

    public function getRememberToken()
    {
        return $this->remember_token;
    }

    public function setRememberToken($value)
    {
        $this->remember_token = $value;
    }

    public function getRememberTokenName()
    {
        return 'remember_token';
    }
}

Although, I defined a foreign key 'user_id', it doesn't automatically fetch the id from user table. How can I fix this?

Answer 1

Firstly you need to add relations to Post.php:

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

And in User.php:

public function posts(){
    return $this->hasMany(Post::class);
}

In DashboardController in action store:

public function store(Request $request)
{
    $post = new Post();
    $post->title = $request->title;
    $post->description = $request->description;

    $user = Auth::user()->id;
    $user->post()->save($post);
    return redirect()->intended('dashboard');
}