Image upload using Arc and nested form

Hi,

I have two models, Product and Category. After help I got from here I could add/edit a product with the chosen category, but now after I set up Arc I face same error again: assign @categories not available in eex template, when I try to add or edit a product. Anyone has an idea what I could have done wrong?

My schemas:

      schema "products" do
        field :avdate, :date
        field :description, :string
        field :name, :string
        field :price, :float
        field :prodimg, ShopifyWeb.DisplayImage.Type
        field :quantity, :integer
        field :subcategory, :integer
        belongs_to :category, Shopify.Departments.Category
        has_many :comments, Shopify.Reviews.Comment
        timestamps()
      end
    
      @doc false
      def changeset(product, attrs) do
        product
        |> cast(attrs, [:name, :quantity, :price, :subcategory, :description, :avdate, :category_id])
        |> cast_attachments(attrs, [:prodimg])
        |> validate_required([:name, :quantity, :price, :subcategory, :description, :avdate, :category_id])
    
      end
 ---
      schema "categories" do
        field :name, :string
        field :subcategory, :string
        has_many :products, Shopify.Inventory.Product
        timestamps()
      end
    
      @doc false
      def changeset(category, attrs) do
        category
        |> cast(attrs, [:name, :subcategory])
        |> validate_required([:name, :subcategory])
      end
New/Edit in product controller:

      def new(conn, _params) do
        changeset = Inventory.change_product(%Product{})
        categories = Repo.all(Category) |> Enum.map(&{&1.name, &1.id})
        render(conn, "new.html", changeset: changeset, categories: categories)
      end
    
      def create(conn, %{"product" => product_params}) do
        case Inventory.create_product(product_params) do
          {:ok, product} ->
            conn
            |> put_flash(:info, "Product created successfully.")
            |> redirect(to: Routes.product_path(conn, :show, product))
    
          {:error, %Ecto.Changeset{} = changeset} ->
            render(conn, "new.html", changeset: changeset)
        end
      end
    
      def show(conn, %{"id" => id}) do
        product = Inventory.get_product!(id)
    
        comment_changeset = Reviews.change_comment(%Comment{})
        render(conn, "show.html", product: product, comment_changeset: comment_changeset)
      end
    
      def edit(conn, %{"id" => id}) do
        product = Inventory.get_product!(id)
        changeset = Inventory.change_product(product)
        categories = Repo.all(Category) |> Enum.map(&{&1.name, &1.id})
        render(conn, "edit.html", product: product,  changeset: changeset, categories: categories)
      end
    
      def update(conn, %{"id" => id, "product" => product_params}) do
        product = Inventory.get_product!(id)
    
        case Inventory.update_product(product, product_params) do
          {:ok, product} ->
            conn
            |> put_flash(:info, "Product updated successfully.")
            |> redirect(to: Routes.product_path(conn, :show, product))
    
          {:error, %Ecto.Changeset{} = changeset} ->
            render(conn, "edit.html", product: product, changeset: changeset)
        end
      end

My image uploader:

      @acl :public_read
      @versions [:primary, :thumbnail]
    
      def transform(:primary, {_file, _product}) do
        {:convert, "-resize 50%"}
      end
    
      def transform(:thumbnail, {_file, _product}) do
        {:convert, "-resize 25%"}
      end
    
      def validate({file, _product}) do
        file_extension = file.file_name
        |> Path.extname()
        |> String.downcase()
    
        Enum.member?([".png"], file_extension)
      end
    
      def s3_object_headers(:primary, {file, _product}) do
        %{content_type: MIME.from_path(file.file_name)}
      end
    
    
    
    
      def default_url(:primary, _product) do
        "http://placehold.it/350x200"
      end
    
      def default_url(:thumbnail, _product) do
        "http://placehold.it/175x100"
      end
    
    end

Display image in product_view.ex

      def display_image(product, version) do
        {product.prodimg, product}
        |> DisplayImage.url(version)
        |> img_tag()
      end
    end

And my product form

    <%= form_for @changeset, @action, [multipart: true], fn f -> %>
      <%= if @changeset.action do %>
        <div class="alert alert-danger">
          <p>Oops, something went wrong! Please check the errors below.</p>
        </div>
      <% end %>
    
      <%= label f, :name %>
      <%= text_input f, :name %>
      <%= error_tag f, :name %>
    
      <%= label f, :quantity %>
      <%= number_input f, :quantity %>
      <%= error_tag f, :quantity %>
    
      <%= label f, :price %>
      <%= number_input f, :price %>
      <%= error_tag f, :price %>
    
      <div class="form-group">
        <%= select f, :category_id, @categories %>
        <p class="help is-danger"><%= error_tag f, :category %></p>
      </div>
    
    
      <%= label f, :subcategory %>
      <%= number_input f, :subcategory %>
      <%= error_tag f, :subcategory %>
    
      <%= label f, :description %>
      <%= text_input f, :description %>
      <%= error_tag f, :description %>
    
      <%= label f, :avdate %>
      <%= date_select f, :avdate %>
      <%= error_tag f, :avdate %>
    
        <div class="form-group">
          <%= label f, :prodimg, class: "control-label" %>
          <%= file_input f, :prodimg, class: "form-control" %>
          <%= error_tag f, :prodimg %>
        </div>
    
    
      <div>
        <%= submit "Save" %>
      </div>
    <% end %>