Laravel Eloquent get relationship with keyBy

Question

I have a Product model with a hasMany relationship

public function pricing()
    {
        return $this->hasMany('App\ProductPrice', 'prod_id', 'id');
    }

I then get the relationship

Product::with('pricing')->all();

How can I retrieve the pricing relationship with the id as the key. I know I can do it on a Collection with keyBy('id) but it doesn't work on a query.

I want to acheive the same results as below but I want to get it from the Product relationship.

ProductPrice::keyBy('id')

Answer 1

A quick workaround is to replace the current relation in you array using setRelation method. In your case:

$product = Product::with('pricing')->all();
$product->setRelation('pricing', $product->pricing->keyBy('id'));

Answer 2

You have to create your own relationship:

<?php

namespace App\Helpers\Classes;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;

class HasManyKeyBy extends HasMany
{
    private $keyBy;

    public function __construct($keyBy, Builder $query, Model $parent, string $foreignKey, string $localKey)
    {
        $this->keyBy = $keyBy;
        parent::__construct($query, $parent, $foreignKey, $localKey);
    }

    public function getResults()
    {
        return parent::getResults()->keyBy($this->keyBy);
    }

    protected function getRelationValue(array $dictionary, $key, $type)
    {
        return parent::getRelationValue($dictionary, $key, $type)->keyBy($this->keyBy);
    }
}

For the sake of simplicity I also recommend you to create a trait:

<?php

namespace App\Helpers\Traits;

use Illuminate\Database\Eloquent\Relations\HasMany;

trait HasManyKeyBy
{
    /**
     * @param $keyBy
     * @param $related
     * @param null $foreignKey
     * @param null $localKey
     * @return HasMany
     */
    protected function hasManyKeyBy($keyBy, $related, $foreignKey = null, $localKey = null)
    {
        // copied from \Illuminate\Database\Eloquent\Concerns\HasRelationships::hasMany

        $instance = $this->newRelatedInstance($related);
        $foreignKey = $foreignKey ?: $this->getForeignKey();
        $localKey = $localKey ?: $this->getKeyName();

        return new \App\Helpers\Classes\HasManyKeyBy($keyBy, $instance->newQuery(),
            $this, $instance->getTable().'.'.$foreignKey, $localKey);
    }
}

Now, you can include this trait into your model, and use $this->hasManyKeyBy protected method:

[...]
class Product extends Model
{
    use HasManyKeyBy;

    public function pricing()
    {
        return $this->hasManyKeyBy('id', ProductPrice::class, 'prod_id', 'id');
    }

    [...]
}