Display subcategory products in main category in laravel

Question

my project has main category - sub category and products. each product has a subcategory_id and each subcategory has a category_id.

now the problem is how to select and show products related to main category. by relations I am getting subcategory products like $subcat->Product, or main category's subcategories like $cat->Subcateogry, but I have no idea how to get products for main category.

for clearing it more:
category (digital goods)
--subcategory (laptop , mobile , tv)
----product (l1 , l2 , m1 , m2 , t1 , t2)

in laptop subcategory view we have l1 and l2 but how is it possible to show them in main category (digital goods).

Answer 1

if your relation setup correctly you could do it using :

nested eager loading

$allProductInMainCategory=MainCategory::where('id',$mainCategoryId)->
with('subCategories.products')->get();

another option is to use nested whereHas

    $allProductInMainCategory=Product::whereHas('subCategory',function($query)use($mainCategoryId){
            $query->whereHas('mainCategory',function($q)use($mainCategoryId)
            {
                $q->where('mainCategories.id',$mainCategoryId);
            });
})->get();