Laravel HasManyThrough or BelongsToMany didn't work in my case. Is it a database structure problem?

Question

I have 3 tables:

products table
-id
- title
- etc.

purchases table
-id
-code
- etc.

purchase_products table
-id
- purchase_id
- product_id
-qty
- etc.

My goal is to retrieve purchases of a single product. The following relationship doesn't work for me. Tried different approaches using belongsToMany also doesn't work.

$this->hasManyThrough(
            Purchase::class,
            PurchaseProduct::class,
            'purchase_id',
            'product_id',
            'id',
            'id'
        );

In a simple way I can get all the purchased products by product_id and then retrieve the purchased items but I need a relationship to make it work in Laravel nova as I want to display the purchased items on the resource .

Answer 1

Product number

class Product {
    public function purchases()
    {
         return $this->belongsToMany(Purchase::class, 'purchase_products', 'product_id', 'purchase_id');
    }
}

Purchase Mode

class Purchase {
    public function products()
    {
         return $this->belongsToMany(Product::class, 'purchase_products', 'purchase_id', 'product_id');
    }
}