title: ActionController::ParameterMissing param is missing or the value is empty
body: <p>I can't solve this problem.
  When I try to use "Chatroom#new" method, I I got this error, <strong>ActionController::ParameterMissing</strong><br>  <strong>param is missing or the value is empty</strong> .</p>
  
  <p>below codes are the ChatroomController.<br></p>
  
  <pre><code>class ChatroomsController &lt; ApplicationController      
      before_action :find_room_owner,only:[:index]
      before_action :objects_for_index,only:[:index]
        def index
          #/users/:user_id/cart/items/chatroom
          sign_in @user if signed_in?
          if @seller &amp;&amp; @buyer
            flash[:success] = "U are owners of the chatroom"
            @messages = Message.all #Messageのmodelを作成
          else
            flash[:error] = "U cant enter the chatroom."
            redirect_to user_cart_items_url(@user,@cart,@items) #@user,@cart,@itemsをgetしろ 
          end
        end
  
        def new
          @user = User.find(params[:user_id])
          @cart = Cart.find(params[:user_id])
          @item = Item.find(params[:item_id])
          @message = Message.new(message_params)
        end
  
        def create 
          @user = User.find(params[:user_id])
          @message = @user.messages.build
          if @message.save
              @message.update_attributes(user_id:@user.id)
              redirect_to user_cart_chatroom_path(@user,@cart,@items)
          else
              flash[:error] = "could not create any message."
              render 'new'
          end
        end
  
      private
  
        def message_params
          params.require(:messages).permit(:id,:user_id,:messages)
          #params{:message =&gt; :id,:user_id,:messages}
        end
  
  
      #before_aciton
        def find_room_owner
          @item = Item.find(params[:item_id])
          @buyer = User.find(params[:user_id])
          @seller = Product.find_by(user_id:@item.user_id)
        end
  
        def objects_for_index
          @user = User.find(params[:user_id])
          @items = Item.all    
        end
  
      end
  </code></pre>
  
  <p>Below codes are the view of Message#new.</p>
  
  <pre><code>&lt;h1&gt;Chatroom#new&lt;/h1&gt;
  &lt;p&gt;Find me in app/views/chatroom/new.html.erb&lt;/p&gt;
  
  
  &lt;%= form_for @message,url:new_user_cart_item_chatroom_path(@user,@cart,@item) do |f| %&gt;
      &lt;%= f.label :messages %&gt;
      &lt;%= f.text_field  :messages %&gt;
  
      &lt;%= f.submit "new message", class:"btn btn-default" %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>Below codes are the migration of Message.</p>
  
  <pre><code>class CreateMessages &lt; ActiveRecord::Migration
    def change
      create_table :messages do |t|
        t.integer :user_id
        t.string :messages
  
        t.timestamps
      end
    end
  end
  </code></pre>
  
  <p>Below codes are the model of message.</p>
  
  <pre><code>class Message &lt; ActiveRecord::Base
  
      validates :messages,presence:true,length:{maximum:200}
      belongs_to :user
  
  end
  </code></pre>
  
  <p>Below codes are the routes.</p>
  
  <pre><code>KaguShop::Application.routes.draw do
  
    resources :users,only:[:show,:new,:create,:edit,:update,:destroy] do
        collection do
          get 'get_images',as:'get_images'
        end
      resources :products,only:[:show,:index,:new,:create,:edit,:update,:destroy] do
        collection do
          post 'add_item', as:'add_item'
          get 'get_image',as:'get_image'
          get 'get_images',as:'get_images'
        end
      end
    end
  
    resources :users,only:[:show,:new,:create,:edit,:update,:destroy] do
      resource :cart,except:[:new,:show,:edit,:destroy,:update,:create] do
        collection do
          post 'purchase', as:'purchase'
          #get 'show' , as: 'show'
          post 'create' , as: 'create'
          #多分routeにas的な感じでtemplateを提供するのが一番いい気がする 
          delete 'destroy',as:'destroy'
          delete 'remove_item',as:'remove_item'
        end
          resources :items,only:[:show,:index] do
            collection do
              get 'get_images',as:'get_images'
            end
              resources :chatrooms,only:[:index,:create,:new] do
              end
          end
      end
    end
  
    resources :sessions,only:[:new,:create,:destroy]
  
  
  
    root 'products#index'
    match '/signup', to:'users#new',via:'get'
    match '/signin', to:'sessions#new', via:'get'
    match '/signout', to:'sessions#destroy', via:'delete'
    match '/contact', to:'nomal_pages#contact', via:'get'
  
  end
  </code></pre>