Laravel 5.5 MassAssignmentException - php

Question

I'm following the Laravel From Scratch tutorial series, I'm currently at the part that you are creating a comment system for your articles system. But I'm having a problem, I don't really know what the error is saying at this point.
The error:
Illuminate\Database\Eloquent\MassAssignmentException
body
The comment model:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Comment extends Model
{
public function post()
{
return $this->belongsTo(Post::class);
}
}
The post model:
<?php
namespace App;
class Post extends Model
{
public function comments()
{
return $this->hasMany(Comment::class);
}
public function addComment($body)
{
$this->comments()->create(compact('body'));
}
}
The route I made:
Route::post('/posts/{post}/comments', 'CommentsController#store');
The comments controller:
<?php
namespace App\Http\Controllers;
use App\Post;
class CommentsController extends Controller
{
public function store(Post $post)
{
$post->addComment(request('body'));
return back();
}
}
Thanks in advance!

Answer 1

Explanation of this error
This is a security feature of Laravel. It is designed to protect you against form manipulation when using mass assignments.
For example on a sign-up form: When you have an is_admin column in your database, a user simply could manipulate your form to set is_admin to true on your server, and therefore in your database. This security feature prevents that by using a whitelist to define safe fields.
How to fix that
You need to set a $fillable property on your model. It's value must be an array containing all fields that are safe to mass assignable (like username, email address, ...).
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Comment extends Model
{
# This property!
protected $fillable = ['body'];
// ...
}
See "Mass assignment" in the docs:
https://laravel.com/docs/5.5/eloquent#mass-assignment

Answer 2

Mass assignment is when you send an array to the model creation, basically setting a bunch of fields on the model in a single go, rather than one by one, something like what you did here:
public function addComment($body)
{
$this->comments()->create(compact('body'));
}
You need to add the field you are populating to the fillable array in Comments.php model:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Comment extends Model
{
protected $fillable = ['body'];
public function post()
{
return $this->belongsTo(Post::class);
}
}
As the documentation states:
You may also use the create method to save a new model in a single
line. The inserted model instance will be returned to you from the
method. However, before doing so, you will need to specify either a
fillable or guarded attribute on the model, as all Eloquent models
protect against mass-assignment by default.
Hope this helps you.