Get Parent from Child in Laravel without extra query - php

Question

I am trying to make a small system with two models: Product, ProductPrice.
Here is the Product model:
class Product extends Model
{
protected $with = ['prices'];
public $tax_rate = 0.2;
public function prices ()
{
return $this->hasMany(ProductPrice::class);
}
}
I put the tax_rate constant here for more clarity, but in real world, it is handled by another relation.
The most important thing here is that the tax_rate is a property of the Product model
Here is the ProductPrice model:
class ProductPrice extends Model
{
protected $appends = ['tax_included_price'];
public function getTaxIncludedPriceAttribute()
{
return (1 + $this->product->tax_rate) * $this->price;
}
public function product ()
{
return $this->belongsTo(Product::class);
}
}
Now let's imagine that I need to use $product->toArray() on some model. With this example, I will get an Exception for infinite loop because my getTaxIncludedPriceAttribute() method makes a new request to find the product attribute.
So could I access the Product parent in the ProductPrice model if I access to it through the parent, and without making an extra query

Answer 1

So, I solved the problem with a handmade solution, not sure of implementation, but it works like I want it to work.
class Product extends Model
{
protected $with = ['pricesRelation'];
protected $appends = ['prices'];
public $tax_rate = 0.2;
public function pricesRelation ()
{
return $this->hasMany(ProductPrice::class);
}
public function getPricesAttribute ()
{
$collection = new Collection();
foreach($this->pricesRelation as $relation) {
$relation->loadProduct($this);
$collection->add($relation);
}
return $relation;
}
}
As you see, I run a $relation->loadProduct($this); to define parent on relation without re querying it...
class ProductPrice extends Model
{
protected $appends = ['tax_included_price'];
protected $loaded_product;
public function getTaxIncludedPriceAttribute()
{
$tax_rate = is_null($loaded_product) ? $this->product->tax_rate : $this->loaded_product->tax_rate;
return (1 + $tax_rate) * $this->price;
}
public function loadProduct (Product $product)
{
$this->loaded_product = $product;
}
public function product ()
{
return $this->belongsTo(Product::class);
}
}