Ruby on rails Rails4：如何使用carrierwave显示和编辑上载的文件？

我可以上传文件并将文件名保存在数据库中。 但是当我编辑时，文件名不会出现

我想：

单击_article.html.erb中的编辑链接时，显示文件名和上载的图像。 在_article.html.erb中显示上载的图像。 第1.rb条

class Article < ActiveRecord::Base
    .
    .
    has_many :photos, dependent: :destroy
    accepts_nested_attributes_for :photos
    .
    .
end

.schema照片

CREATE TABLE "photos" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, 
"article_id" integer, 
"image" varchar(255), 
"created_at" datetime, 
"updated_at" datetime);

文章\u controller.rb

class ArticlesController < ApplicationController
    .
    .
  def new
    @article = Article.new
    @article.photos.build
    .
    .
  end

  def create
    @article = current_user.articles.build(article_params)
    .
    .
  end

  def edit
    @article = Article.find(params[:id])
  end

  def update
    @article = Article.find(params[:id])
    if @article.update(article_params)
      redirect_to current_user
    else
      render 'edit'
    end
  end
    .
    .
  private

    def article_params
      params.require(:article).permit(:content, photos_attributes: [:id, :article_id, :image])
    end
    .
    .
end

articles\\u article.html.erb

我想在点击编辑链接_article_form.html.erb后在这里显示上传的图像和文件名

articles\edit.html.erb

<h1>Update article</h1>
<div class="row">
        <%= render 'shared/article_form' %>
</div>

共享\\u article\u form.html.erb

编辑时，将显示：内容。但是：没有选择图像文件

当我提交新文章时，development.log

Started POST "/articles" for 127.0.0.1 at 2014-07-05 16:31:11 +0900
Processing by ArticlesController#create as HTML
  Parameters: {"utf8"=>"?","authenticity_token"=>"uaWcqBZ6rhS/NIal/...=", "article"=>{"category_id"=>"6", "content"=>"last", "photos_attributes"=>{"0"=>{"article_id"=>"", "image"=>#<ActionDispatch::Http::UploadedFile:0x3cb0910 @tempfile=#<File:C:/.../AppData/Local/Temp/RackMultipart20140705-6112-1q9t7r6>, @original_filename="DSCN0721_080.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"article[photos_attributes][0][image]\"; filename=\"DSCN0721_080.JPG\"\r\nContent-Type: image/jpeg\r\n">}}}, "commit"=>"Post"}
  [1m[35mUser Load (1.0ms)[0m  SELECT "users".* FROM "users" WHERE "users"."remember_token" = '...' LIMIT 1
  [1m[36m (0.0ms)[0m  [1mbegin transaction[0m
  [1m[35mSQL (3.0ms)[0m  INSERT INTO "articles" ("content", "created_at", "category_id", "updated_at", "user_id") VALUES (?, ?, ?, ?, ?)  [["content", "last"], ["created_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["category_id", 6], ["updated_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["user_id", 1]]
  [1m[36mSQL (27.0ms)[0m  [1mINSERT INTO "photos" ("article_id", "created_at", "image", "updated_at") VALUES (?, ?, ?, ?)[0m  [["article_id", 306], ["created_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["image", "DSCN0721_080.JPG"], ["updated_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00]]
  [1m[35m (5.0ms)[0m  commit transaction
Redirected to http://localhost:3000/users/1
Completed 302 Found in 128ms (ActiveRecord: 36.0ms)

---

我之前也遇到过同样的问题，但没有找到任何解决办法。我所做的就是在这里

<%= form_for(@article) do |f| %>
  <div class="field">
    <%= f.text_area :content, placeholder: "Compose new article..." %>
    <%= f.fields_for :photos, @article.photos do |p| %>
      <%= p.hidden_field :article_id %>
      <%= p.label :image %>
      <% if p.object.image %>
        <%= image_tag p.object.image.url %>
        <p><%= p.object.image.file.filename %></p>
      <% end %>
      <%= p.file_field :image %>
    <% end %>
  </div>
  <%= f.submit "Post", class: "btn btn-large btn-primary" %>
<% end %>

即使您试图通过js将图像文件名设置为file_字段，也会出现以下错误

未能在“HTMLInputElement”上设置“value”属性：此输入 元素接受一个文件名，该文件名只能通过编程设置为 空字符串

---

你能在提交表格时发布日志中生成的参数吗？Pavan，谢谢你的及时回复。虽然我在提交新文章时更新了development.log，但我不知道下一步该怎么办。谢谢，拉胡尔·辛格。将显示文件名和图像！！但我也想知道如何显示文件名，而不是消息no file selected（未选择文件）。一种方法是，隐藏文件字段并添加一个按钮，然后通过js单击按钮单击文件字段。并通过js将文件名替换为新选择的文件。我还没有尝试您的最新评论，但我在调用new.html.erb（与articles\edit.html.erb.change if condition with Rahul Singh相同）时发现articles中的NoMethodError为nil:NilClass添加了新的未定义方法'filename'，非常感谢你的回答。它起作用了！

<h1>Update article</h1>
<div class="row">
        <%= render 'shared/article_form' %>
</div>

<%= form_for(@article) do |f| %>
  <div class="field">
    <%= f.text_area :content, placeholder: "Compose new article..." %>
    <%= f.fields_for :photos do |p| %>
      <%= p.hidden_field :article_id %>
      <%= p.label :image %>
      <%= p.file_field :image %>
    <% end %>
  </div>
  <%= f.submit "Post", class: "btn btn-large btn-primary" %>
<% end %>

Started POST "/articles" for 127.0.0.1 at 2014-07-05 16:31:11 +0900
Processing by ArticlesController#create as HTML
  Parameters: {"utf8"=>"?","authenticity_token"=>"uaWcqBZ6rhS/NIal/...=", "article"=>{"category_id"=>"6", "content"=>"last", "photos_attributes"=>{"0"=>{"article_id"=>"", "image"=>#<ActionDispatch::Http::UploadedFile:0x3cb0910 @tempfile=#<File:C:/.../AppData/Local/Temp/RackMultipart20140705-6112-1q9t7r6>, @original_filename="DSCN0721_080.JPG", @content_type="image/jpeg", @headers="Content-Disposition: form-data; name=\"article[photos_attributes][0][image]\"; filename=\"DSCN0721_080.JPG\"\r\nContent-Type: image/jpeg\r\n">}}}, "commit"=>"Post"}
  [1m[35mUser Load (1.0ms)[0m  SELECT "users".* FROM "users" WHERE "users"."remember_token" = '...' LIMIT 1
  [1m[36m (0.0ms)[0m  [1mbegin transaction[0m
  [1m[35mSQL (3.0ms)[0m  INSERT INTO "articles" ("content", "created_at", "category_id", "updated_at", "user_id") VALUES (?, ?, ?, ?, ?)  [["content", "last"], ["created_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["category_id", 6], ["updated_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["user_id", 1]]
  [1m[36mSQL (27.0ms)[0m  [1mINSERT INTO "photos" ("article_id", "created_at", "image", "updated_at") VALUES (?, ?, ?, ?)[0m  [["article_id", 306], ["created_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00], ["image", "DSCN0721_080.JPG"], ["updated_at", Sat, 05 Jul 2014 07:31:11 UTC +00:00]]
  [1m[35m (5.0ms)[0m  commit transaction
Redirected to http://localhost:3000/users/1
Completed 302 Found in 128ms (ActiveRecord: 36.0ms)

<%= form_for(@article) do |f| %>
  <div class="field">
    <%= f.text_area :content, placeholder: "Compose new article..." %>
    <%= f.fields_for :photos, @article.photos do |p| %>
      <%= p.hidden_field :article_id %>
      <%= p.label :image %>
      <% if p.object.image %>
        <%= image_tag p.object.image.url %>
        <p><%= p.object.image.file.filename %></p>
      <% end %>
      <%= p.file_field :image %>
    <% end %>
  </div>
  <%= f.submit "Post", class: "btn btn-large btn-primary" %>
<% end %>