我正在使用 Carrierwave 将图像字段添加到基于 Ryan Bates 修订的 #196 截屏视频的 Rails 嵌套模型中。Carrierwave 位基于他的截屏视频 #253
问题和答案模型嵌套在类别模型中。
我可以让图像上传并显示在“显示”页面上。但是当我返回编辑视图时，没有图像，我仍然看到选择文件按钮旁边的“未选择文件”文本。我可以来回切换到 Show 页面，它仍然出现在 Show 中，但永远不会出现在 Edit 中。我的用户会认为他们每次都必须上传新图片！
我的显示视图中有这行代码：
<%= image_tag question.image_url(:thumb).to_s if question.image? %>
但是如果我尝试将其放入 _form 视图中，则会出现未知的局部变量或方法错误。
我已经尝试了几个 if 语句，但没有得到它的工作。我试图把它全部放在编辑视图中，但无济于事。
我的 _form 视图：
<%= form_for @category, :html => {:multipart => true} do |f| %>
<% if @category.errors.any? %>
<div class="error_messages">
<h2><%= pluralize(@category.errors.count, "error") %> prohibited this category from being saved:</h2>
<ul>
<% @category.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div id="categorytitle" class="field">
<%= f.label :name, "Category Name" %><br />
<%= f.text_field :name %>
</div>
<%= f.fields_for :questions do |builder| %>
<%= render 'question_fields', f: builder %>
<% end %>
<%= link_to_add_fields "Add Question", f, :questions %>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
我的 _questions 部分
<fieldset id="questionarea">
<%= f.label :content, "Question" %>
<%= f.text_field :content%>
<hr>
<div class="field">
<p>
<%= f.check_box :active, class: "pull-left" %>
<%= f.label :active %>
<span class="help-block">Turning questions on and off helps you customize the category.</span>
</p>
</div>
<hr>
<div class="field clearthat">
<%= f.label :image, "Add an Image"%>
<span class="help-block">Images will help non-readers understand the question.</span>
<%= f.file_field :image %>
<%= f.hidden_field :image_cache %>
</div>
<hr>
<!-- <%= link_to "remove", '#', class: "remove_fields" %> -->
<p class="clearthat"> </p>
<%= f.fields_for :answers do |builder| %>
<%= render 'answer_fields', f: builder %>
<% end %>
<%= link_to_add_fields "Add Answer", f, :answers %>
</fieldset>
有一个 _answer 部分，但似乎没有考虑到它。
这是我尝试将图像直接放入我的 _question 部分时收到的错误消息（从上面的 _question 代码的中心截取）：
<div class="field clearthat">
<%= f.label :image, "Add an Image"%>
<span class="help-block">Images will help non-readers understand the question.</span>
<%= image_tag question.image_url(:thumb).to_s if question.image? %>
<%= f.file_field :image %>
<%= f.hidden_field :image_cache %>
</div>
这是我得到的错误：
NameError in Categories#edit
undefined local variable or method `question'
我的类别模型：
class Category < ActiveRecord::Base
attr_accessible :name, :questions_attributes
has_many :questions
accepts_nested_attributes_for :questions, allow_destroy: true
end
我的问题模型：
class Question < ActiveRecord::Base
attr_accessible :content, :category_id, :answers_attributes, :active, :image, :image_cache
belongs_to :category
has_many :answers
accepts_nested_attributes_for :answers, allow_destroy: true
mount_uploader :image, ImageUploader
end
我的类别控制器：
class CategoriesController < ApplicationController
before_filter :signed_in_user, only: [:index, :edit, :update, :destroy]
before_filter :correct_user, only: [:edit, :update]
before_filter :admin_user, only: :destroy
def index
@categories = Category.all
end
def show
@category = Category.find(params[:id])
end
def new
@category = Category.new
end
def create
@category = Category.new(params[:category])
if @category.save
redirect_to @category, :notice => "Successfully created category."
else
render :action => 'new'
end
end
def edit
@category = Category.find(params[:id])
end
def update
@category = Category.find(params[:id])
if @category.update_attributes(params[:category])
redirect_to @category, :notice => "Successfully updated category."
else
render :action => 'edit'
end
end
def destroy
@category = Category.find(params[:id])
@category.destroy
redirect_to categories_url, :notice => "Successfully destroyed category."
end
private
def signed_in_user
unless signed_in?
store_location
redirect_to signin_path, notice: "Please sign in."
end
end
def correct_user
@user = User.find(params[:id])
redirect_to(root_path) unless current_user?(@user)
end
def admin_user
redirect_to(root_path) unless current_user.admin?
end
结尾
感谢任何能提供帮助的人。