Collection Customization in Laravel Using CollectedBy

When working with Eloquent collections, you might need to add specific functionality that applies only to certain model types. Laravel's new CollectedBy attribute provides a declarative way to customize collections without overriding model methods, making your code more maintainable and intention-clear.

Previously, customizing model collections required overriding the newCollection() method, but this new attribute-based approach offers a cleaner solution at the class level.

use Illuminate\Database\Eloquent\Attributes\CollectedBy;

#[CollectedBy(CustomCollection::class)]
class YourModel extends Model
{
    // Model implementation
}

Let's explore a practical example with an e-commerce product catalog:

// Product Collection
<?php

namespace App\Collections;

use Illuminate\Database\Eloquent\Collection;

class ProductCollection extends Collection
{
    public function inStock()
    {
        return $this->filter(fn($product) => $product->stock_count > 0);
    }

    public function onSale()
    {
        return $this->filter(fn($product) => $product->discount_percentage > 0);
    }

    public function byPriceRange($min, $max)
    {
        return $this->filter(function($product) use ($min, $max) {
            $price = $product->getEffectivePrice();
            return $price >= $min && $price <= $max;
        });
    }

    public function topRated()
    {
        return $this->filter(fn($product) => $product->average_rating >= 4)
            ->sortByDesc('average_rating');
    }
}

//Product model
namespace App\Models;

use App\Collections\ProductCollection;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Attributes\CollectedBy;

#[CollectedBy(ProductCollection::class)]
class Product extends Model
{
    public function getEffectivePrice()
    {
        if ($this->discount_percentage > 0) {
            return $this->price * (1 - $this->discount_percentage / 100);
        }
        
        return $this->price;
    }
}