Simple tag trait for Laravel models

Tags are very common in any application. This snippet leverages Eloquent's polymorphism to give any model taggable capabilities.

Usage

$model->addTag('trending')->addTag('wonderful');
$model->hasTag('trending'); // true
$model->hasAnyTag('important', 'valuable', 'woderful'); // true
$model->removeTag('trending');

Implementation

app/HasTags.php

<?php

namespace App;

use App\Tag;
use Illuminate\Support\Arr;

trait HasTags
{
    public function tags()
    {
        return $this->morphToMany(Tag::class, 'taggable');
    }

    public function hasTag($tag): bool
    {
        return $this->tags()->get()->contains(Tag::wrap($tag));
    }

    public function hasAnyTag(...$tags): bool
    {
        foreach (Arr::flatten($tags) as $tag) {
            if ($this->hasTag($tag)) {
                return true;
            }
        }

        return false;
    }

    public function addTag(...$tag): void
    {
        foreach (Arr::flatten($tag) as $tag) {
            $this->tags()->attach(Tag::wrap($tag));
        }
    }

    public function removeTag(...$tag): void
    {
        foreach (Arr::flatten($tag) as $tag) {
            $this->tags()->detach(Tag::wrap($tag));
        }
    }
}

---

app/Tag.php

<?php

namespace App;

use App\HasName;
use Illuminate\Database\Eloquent\Model;

class Tag extends Model
{
    use HasName;

    protected $fillable = [
        'name',
    ];

    public function __toString()
    {
        return (string) $this->name;
    }

    public function posts()
    {
        return $this->morphedByMany(Post::class, 'taggable');
    }

    public function setNameAttribute($value)
    {
        if (! preg_match($regex = '/^[a-z0-9_]+$/', $value)) {
            throw new \InvalidArgumentException("invalid tag format: {$value} (it should match $regex)");
        }

        $this->attributes['name'] = $value;
    }
}

Note: for the HasName trait, see this post

---

app/Post.php

<?php

namespace App;

class Post
{
    use Taggable;

    // ...
}

Bonus

Here's a JavaScript function to cleanup a tag input in the front-end:

function cleanupTag(tag) {
    // see https://stackoverflow.com/a/37511463/381220
    return tag.toLowerCase()
        .normalize("NFD").replace(/[\u0300-\u036f]/g, "")
        .replace(/[^a-z0-9_]*/g, '');
}