Rails：如何在另一个命名空间中的控制器中创建类对象？答案

【问题标题】：Rails : How to create an object of class within a controller which is in another namespace?Rails：如何在另一个命名空间中的控制器中创建类对象？
【发布时间】：2017-12-13 06:18:35
【问题描述】：

我正在使用 CarrierWave 从 AngularJS 客户端上传文件。为 carrierWave 生成的 uploader 位于 另一个命名空间，而 controller 位于 另一个命名空间。

因此，当我尝试在 controller 中创建 上传器 的 object 时，我得到了以下错误：

uninitialized constant Api::V1::ProductsController::FileUploader

这是我的目录结构：

app
|--controllers
   |--api
      |--controllers
         |--api
            |--v1
               |--products_controller.rb
|--uploaders
   |--file_uploader.rb

产品控制器

  class Api::V1::ProductsController < ApplicationController
    respond_to :json

  ......

  def createFromExcel
    puts "------------------------------------"
    puts params[:file]
    puts "------------------------------------"
    uploader = FileUploader.new
    uploader.store!(params[:file])
  end


end

FileUploader 类：

class FileUploader < CarrierWave::Uploader::Base

  # Include RMagick or MiniMagick support:
  # include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  # def default_url(*args)
  #   # For Rails 3.1+ asset pipeline compatibility:
  #   # ActionController::Base.helpers.asset_path("fallback/" + [version_name, "default.png"].compact.join('_'))
  #
  #   "/images/fallback/" + [version_name, "default.png"].compact.join('_')
  # end

  # Process files as they are uploaded:
  # process scale: [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  # version :thumb do
  #   process resize_to_fit: [50, 50]
  # end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
   def extension_whitelist
     %w(xlsx xls)
   end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

end

如何在我的 Controller 中创建 FileUploader 类 的对象？

【问题讨论】：

为什么需要在控制器中创建它？ Carrierreave 适用于您的模型；你用mount_uploader设置模型了吗？
我不想要永久存储，我只需要遍历电子表格并读取数据并将其保存到数据库中。
尝试将require 'uploaders/file_uploader'添加到控制器

标签： ruby-on-rails ruby file-upload ruby-on-rails-5 carrierwave

【解决方案1】：

尝试使用uploader = ::FileUploader.new

【讨论】：

【解决方案2】：

要引用来自main（“全局命名空间”）而不是当前模块嵌套（“命名空间”）的常量，请使用::

class Api::V1::ProductsController < ApplicationController
  respond_to :json

  # use snake_case not camelCase
  def create_from_excel
    uploader = ::FileUploader.new
    uploader.store!(params[:file])
  end
end

见：

【讨论】：