无法在嵌套模型编辑页面中的_form视图中显示图像

Question

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

问答模型嵌套在类别模型中.

我可以将图像上传并显示在"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.我可以前往Show页面来回播放它仍然出现在Show中,但从不出现在Edit中.我的用户会认为他们每次都要上传新图片!

我的Show视图中有这行代码:

<%= image_tag question.image_url(:thumb).to_s if question.image? %>

但如果我尝试将其放入_form视图,那么我会得到一个未知的局部变量或方法错误.

我已经尝试了几个if语句,但还没有让它工作.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">&nbsp;</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,但似乎没有形成它.

这是我尝试将图像直接放入我的_question部分时得到的错误消息(从上面_question代码的中心剪切):

<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'

我的分类型号:

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

结束

感谢任何能提供帮助的人.

Answer 1

也许我的问题没有得到很好的解答,因为我没有得到任何帮助.但我终于明白了!

这是导致问题的代码行:

<%= image_tag question.image_url(:thumb).to_s if question.image? %>

这是有效的代码行:

<%= image_tag f.object.image_url(:thumb) %>

我并不完全清楚,但似乎我在我的问题部分,并调用一个称为问题的方法,rails并不知道我的意思.

我在这个stackoverflow QA中找到了答案:Rails嵌套表单与图像

现在我有一个工作if语句,所以我的用户可以更改图像:

<% if f.object.image? %>
  <%= image_tag f.object.image_url(:thumb) %>
  <%= f.file_field :image %>
<% else %>
  <%= f.file_field :image %>
  <%= f.hidden_field :image_cache %>
<% end %>

接下来,我必须弄清楚如何更改file_field按钮上的值.