检查“poster_file_name”缺少必需的poster_file_name模型

Question

我正在构建一个非常简单的应用程序，允许用户发布评论和评论，其模型如下：

• 用户只有一个id、名称和电子邮件，并且有许多评论和评论。
• 评论有一个id，标题，内容，用户id，有多个注释，属于一个用户。
• 注释有一个id，内容，审查id，用户id，属于一个用户和一个评论。

没有认证系统。

到目前为止，该应用程序正在运行。

现在，我正在尝试添加一个功能，允许用户在添加评论时上传图片(电影海报)。

所以，遵循这个教程

我安装了最新版本的ImageMagik和剪纸夹，

我在评审模型中添加了以下内容：

class Review < ActiveRecord::Base
  has_attached_file :poster, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => "/images/:style/missing.png"
  validates_attachment_content_type :poster, :content_type => /\Aimage\/.*\Z/
end

我运行了以下迁移：

rails generate paperclip review poster

显示在我的终端上：

MacBook-Pro-de-Thibaud-CLEMENT:moview Thibaud$ rails generate paperclip review poster
/Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/generators/actions/create_migration.rb:13:in `migration_file_name': protected method `migration_file_name' called for #<PaperclipGenerator:0x007fac51501428> (NoMethodError)
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/generators/actions/create_migration.rb:34:in `existing_migration'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:112:in `invoke_with_conflict_check'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/actions/create_file.rb:60:in `invoke!'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/actions.rb:94:in `action'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/generators/migration.rb:36:in `create_migration'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/generators/migration.rb:65:in `migration_template'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/paperclip-4.1.1/lib/generators/paperclip/paperclip_generator.rb:16:in `generate_migration'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/command.rb:27:in `run'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/invocation.rb:126:in `invoke_command'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `block in invoke_all'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `each'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `map'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `invoke_all'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/group.rb:232:in `dispatch'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/thor-0.19.1/lib/thor/base.rb:440:in `start'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/generators.rb:156:in `invoke'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/commands/generate.rb:11:in `<top (required)>'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `require'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `block in require'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:214:in `load_dependency'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `require'
    from /Users/Thibaud/.rvm/gems/ruby-2.0.0-p451@railstutorial_rails_4_0/gems/railties-4.0.5/lib/rails/commands.rb:48:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

然后跑了：

rake db:migrate

我停止并重新启动了我的服务器。

我用以下行编辑了我的Review#Edit视图文件：

<%= form.file_field :poster %>

我更新我的审核控制器：

def review_params
      params.require(:review).permit(:title, :poster, :content, :user_id)
    end

我补充说

<%= image_tag @review.poster.url(:medium) %>

Review#Index和Review#Show的

当我访问Review#Index页面时，应用程序就可以工作了。

当我访问Review#Edit页面时，应用程序也能工作:它显示一个字段来上传图像。

但是，只要单击“更新审查”按钮，就会收到以下错误消息：

​

​

我怎么才能把这事做好？

Answer 1

如前所述，生成剪纸夹迁移的protected_method错误是已知的问题，目标是包含在4.1.2版本中。

如果您不愿意修改您的Gemfile，从而避免可能导致副作用的任何其他边缘更改，则只需手动创建您自己的迁移：

class AddPosterColumnsToReviews < ActiveRecord::Migration
  def self.up
    add_attachment :reviews, :poster
  end

  def self.down
    remove_attachment :reviews, :poster
  end
end

这正是发电机所要做的。创建它之后，只需正常运行rake db:migrate即可。