create a post with pre-defined categories - laravel

Question

I have a table for posts and a table for categories. But its not possible to create new categories they should already exist in the database and is not possible to change them. DO you know how to structure this logic properly on laravel?
Also when a post is created it should have a maximum of 3 categories and a published date. Do you know how to do that validation in laravel, of dates and the maximum of 3 categories when a post is created? I have this validation for now:
$this->validate($request, [
‘post_name’ => 'required|max:255',
‘post_categories’ => 'required',
‘post_date' => 'required',
]);
Relevant code for this context:
// Category Model:
class Category extends Model
{
public function posts(){
return $this->belongsToMany('App\Post’);
}
}
// Post model
class Post extends Model
{
public function categories(){
return $this->belongsToMany('App\Category');
}
}
Migration Post:
class CreatePost extends Migration
{
public function up()
{
Schema::create(‘posts’, function (Blueprint $table) {
$table->increments('id');
$table->string(‘name’);
…
$table->timestamps();
});
}
Migration Category:
<?php
class CreateCategoriesTable extends Migration
{
public function up()
{
Schema::create('categories', function (Blueprint $table) {
$table->increments('id');
$table->string('name');
$table->timestamps();
});
}
}
// post controller
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
class PostController extends Controller
{
public function index()
{
}
public function create()
{
return view(‘app.createPost’);
}
public function store(Request $request)
{
dd($request->all());
$this->validate($request, [
‘post_name’ => 'required|max:255',
‘post_categories’ => 'required',
‘post_date' => 'required',
]);
}

Answer 1

Use between rule
'post_categories' => 'required|array|between:1,3'
And for the first question, use firstOrCreate
foreach($request->post_categories as $categoryName){
$category= App\Category::firstOrCreate(['name' => $categoryName]);
$post->categories->attach($category->id);
}