gistfile1.txt

  <% categories.each do |category| %>
    <% card_ids = [] %>
    <% cards = Card.joins(:card_types).where(card_types: {id: category.card_type_ids}) %>
    <% cards.find_each do |card| %>
      <% card_ids << card.id unless card_ids.include?(card.id) %>
    <% end %>
    <% category_cards = @main_cards.where(card_id: [card_ids]) %>
  <% end %>