make-columns-visible.php

<?php

protected $hidden = ['published_at'];

static::creating(function (Post $post) {
    $post->visible('published_at');
  
    Validator::validate($post->toArray(), static::$rules);
});

PostModelEvents.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Str;

class Post extends Model
{
    public static function boot()
{
    parent::boot();

static::creating(function (Post $post) {
    if (! $post->slug) {
	$post->slug = Str::slug($post->title);
    }
});
}
}

PostWithValidation.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Str;
use Illuminate\Support\Facades\Validator;

class Post extends Model
{
    public static $rules = [
        'title' => 'required|string|max:255',
        'slug' => 'required|string',
        'excerpt' => 'nullable|string|max:160',
        'published_at' => 'nullable|date',
    ];
    
    public static function boot()
	{
	    parent::boot();
        
        static::creating(function (Post $post) {
            Validator::validate($post->toArray(), static::$rules);
        });
	}
}