carrierwave白名單錯誤未顯示

Question

在我的Rails應用程序中，我已獲得carrierwave gem上傳內容。現在我想fileformats

的驗證，所以我一直在上傳添加了這個：

def extension_white_list 
%w(jpg jpeg gif png) 
end 

當我試圖把它上傳不到風度上傳PDF格式的PDF，但沒有錯誤打印到屏幕上。什麼不見​​了？

我認爲頁面應該回去，所以用戶有機會選擇不同的文件？

感謝

UPDATE - 表格查看代碼：

<%= form_for(@channel, :html => {:multipart => true, :class => "form-horizontal", :role => "form"}, :method => :post, :url => url_for(controller: 'channels', action: 'edit', id: @channel.id)) do |f| %> 
     <div class="col-md-4"> 
     <div class="form-group col-md-12"> 
      <label><%= f.label :channelimage %></label> 
      <%= f.file_field :channelimage, :class => "form-control", :placeholder => :image%> 
      <br> 
      <% if @channel.channelimage.present? %> 
       <div clasS="thumbnail"> 
       <img src="<%= @channel.channelimage %>" alt="<%= @channel.channelname %>"/> 
       </div> 
      <% end %> 
     </div> 
     </div> 

UPDATE：控制器功能

#Speichert die geänderten Werte eines Channels 
def edit 
    @user = User.find_by_id session[:user_id] 
    @knowledgeproviderList = @user.knowledgeprovider 
    @channel = Channel.find params[:id] 
    @channelList = Channel.where(knowledgeprovider_id: @knowledgeproviderList.pluck(:id)) 
    if request.post? 
    @channel.update_attributes(channel_edit_params) 
    if @channel.save 
     flash[:notice] = t("flash.saved") 
     redirect_to action: :index 
    else 
     redirect_to action: :edit, :id => @channel.id 
    end 
    end 
end 

Answer 1

Validation - Guides

所以基本上你不輸出錯誤，所以使用您需要添加的指南格式：

<% if @channel.errors.any? %> 
    <div id="error_explanation"> 
    <h2> 
     <%= pluralize(@channel.errors.count, "error") %> prohibited 
     this channel from being saved: 
    </h2> 
    <ul> 
     <% @channel.errors.full_messages.each do |msg| %> 
     <li><%= msg %></li> 
     <% end %> 
    </ul> 
    </div> 
<% end %>