Aggregate relationships in Laravel

What? - Laravel already has relationships

Laravel can make relationships to other models, but not to scalars (e.g. numbers). This package can COUNT() and SUM() relationships. Especially COUNT() is useful, because duh.

Why? - Laravel has this!

No. The only way in Laravel to count a relationship is with withCount(), which...

• only work for eager loading, not lazy
• can't be called after the objects exists, on the collection (like ->load('name'))
• are always named {name}_count

How?

Add the trait to your models/base model:

use RelatesToAggregates;

This exposes methods hasCount(relatedClass, foreignKey), hasAggregate(relatedClass, aggregateColumn, foreignKey) and hasManyScalar(targetKey, targetTable, foreignKey):

Define the relationship:

class User extends Model {
	use RelatesToAggregates;

	// Number of transactions for this user
	function num_transactions() {
		return $this->hasCount(Transaction::class, 'user_id');
	}

	// Sum of all positive and negative transactions for this user
	function current_balance() {
		return $this->hasAggregate(Transaction::class, 'sum(money_change)', 'user_id');
	}

	// List of payment uuids
	function payment_refs() {
		return $this->hasManyScalar('reference_uuid', 'transactions', 'user_id');
	}
}

And then eager load it like normal relationships:

$users = User::with(['address', 'fav_color', 'num_transactions', 'current_balance', 'payment_refs'])->get();

or later, like normal relationships, unlike Laravel's count:

$users = User::all();
$users->load(['address', 'fav_color', 'num_transactions', 'current_balance', 'payment_refs']);

and if you can't/don't want to eager load it, lazy load it, like a normal relationship:

$user = User::find(123);
echo "Balance: {$user->current_balance} ({$user->num_transactions} transactions): " .
	implode(', ', $user->payment_refs);

Recap

• Eager AND lazy loading
• Eager loadable on existing collection
• Custom names

Like a real relationship!