laravel - Has many through many-to-many

Question

I have the following table layout:

deals:
- id
- price

products:
- id
- name

deal_product:
- id
- deal_id
- product_id

metrics:
- id
- name

metric_product:
- id
- metric_id
- product_id
- value

products and metrics have a many-to-many relationship with a pivot column of value.

deals and products also have a many-to-many relationship.

I can get metrics for a product with $product->metrics, but I want to be able to get all metrics for all products related to a deal, so I could do something like this: $deal->metrics.

I currently have the following in my Deal model:

public function metrics()
{
    $products = $this->products()->pluck('products.id')->all();

    return Metric::whereHas('products', function (Builder $query) use ($products) {
        $query->whereIn('products.id', $products);
    });
}

But this doesn't return a relationship, so I cannot eager load it or get related models from it.

It needs to be in relationship format, because they need to be eager loaded for my use case.

Thanks for your help!

Answer 1

If you want to have a custom relation, you can create your own extends to Relation abstract class. For example: BelongsToManyThought.

But if you don't want to implement a Relation, I think that it can fulfill your needs :

In AppDeal.php, you can combine the solution of @thomas-van-der-veen

public function metrics()
{
    return Metric

    ::join('metric_product', 'metric.id', '=', 'metric_product.metric_id')

    ->join('products', 'metric_product.product_id', '=', 'products.id')

    ->join('deal_product', 'products.id', '=', 'deal_product.product_id')

    ->join('deals', 'deal_product.deal_id', '=', 'deal.id')

    ->where('deal.id', $this->id);

}


// you can access to $deal->metrics and use eager loading
public function getMetricsAttribute()
{
    if (!$this->relationLoaded('products') || !$this->products->first()->relationLoaded('metrics')) {
        $this->load('products.metrics');
    }

    return collect($this->products->lists('metrics'))->collapse()->unique();
}

You can refer to this post to see how you can simply use nested relations.

This solution can do the trick for querying relation with method and access to metrics attribute.