First argument in form cannot contain nil or be empty in a rails form -

i getting mad cause have situation trying modify quantity of item via custom action , don´t know why works in 1 view doesn´t in another, stupid can´t find reason, action add_item works perfectly, update_item_quantity doesn´t display de view , shows exception:

first argument in form cannot contain nil or empty 

here code:

routes.rb:

  resources :designs   resources :carts   resources :cart_items     :add_to_cart, on: :member     post :add_item, on: :member     post :update_item_quantity, on: :member   end 

te controllers following:

cart_items_controller.rb

def add_item     @cart_item = cartitem.new(add_item_params)     @design = design.find(params[:design_id])     @cart = cart.find(current_user.cart_id)      @cart_item.design_id = @design.id     @cart_item.cart_id = current_user.cart_id     if @cart_item.save         flash[:success] = "design succesfully added active cart"         redirect_to cart_path(@cart)     else         flash[:danger] = "design couldn´t added cart"         redirect_to designs_path     end end  def update_item_quantity     @cart = cart.find(current_user.cart_id)     @cart_item= cartitem.find(params(:cart_item_id))       redirect_to cart_path(@cart) end  private  def add_item_params     params.require(:cart_item).permit(:quantity) end 

and views are:

/cart_items/add_to_cart.html.erb:

<div class="container body-content">     <div class="row col-md-12">         <p>add design: <%= @design.name %></p>     </div>     <% if current_user.cart_active? %>         <div class="col-md-4 tdp-add-to-cart-panel">             <p>click on button below if want add design cart have active @ moment</p>             <%= form_for @cart_item, url: {controller: 'cart_items', action: "add_item", params: {design_id: @design.id}} |f| %>             <span class="">qty: </span>             <span class=""><%= f.number_field (:quantity, min: '1', max: '100', step: '1') %></span>             <span class=""><%= f.submit "add design", class: "btn btn-login" %></span>             <% end %>             <%#= button_to "add current cart", {:controller => :carts, :action => :add_item_to_active_cart, :design_id => @design.id }, class: "btn-lg btn-login" %>         </div>         <div class="col-md-4"></div>         <div class="col-md-4"></div>     <% else %>         <div class="col-md-6"></div>         <div class="col-md-6"></div>     <% end %> </div> 

and here /carts/show.html.erb

<h2>cart, <%= @cart.name %></h2>      <div class="col-md-8 tdp-listing cart-content-listing">         <% @cart_items.each |ci|  %>             <div class="row tdp-listing-row">                 <div class="col-md-6">                     <%= ci.design.name %>                 </div>                 <div class="col-md-2">                     <%= ci.design.price * ci.quantity %>                 </div>                 <div class="col-md-3">                     <%= form_for @cart_item, url: {controller: "cart_items", action: "update_item_quantity", params: {cart_item_id: ci.id}} |f| %>                         <span class="">qty: ci.id <%= ci.id %> </span>                         <span class=""><%#= f.number_field(:quantity, min: '1', max: '100', step: '1') %></span>                         <span class=""><%#= f.submit "update", class: "btn btn-login" %></span>                     <% end %>                 </div>                 <div class="row col-md-1">                     <%= link_to "delete", cart_item_path(ci), method: :delete,                                  data: { confirm: "are sure want delete item?" }, class: "btn btn-xs btn-danger" %>                 </div>             </div>         <% end %>     </div> 

wait news , in advance.

antonio

please add code cartscontroller#show action whole exception message too.

i guess have not assigned value instance variable @cart_items in show action. that's why <% @cart_items.each |ci| %> on line 4 failing assign value ci in /carts/show.html.erb template.

this should reason why form throwing exception containing nil value.