在Rails4中使用carrierwave-mongoid上传文件

在Rails4和Mongoid4中，使用MongoDB's GridFS存储文件。

步骤1：在Gemefile文件中添加carrierwave-mongoid。

gem 'mongoid', git: 'https://github.com/mongoid/mongoid.git'
gem 'mongoid-grid_fs', github: 'ahoward/mongoid-grid_fs'
gem 'carrierwave', :git => "git://github.com/jnicklas/carrierwave.git"
gem 'carrierwave-mongoid', :require => 'carrierwave/mongoid'
gem 'mini_magick', :git => 'git://github.com/probablycorey/mini_magick.git'

步骤2：创建carrierwave的配置文件config/initializers/carrierwave.rb。

#config/initializers/carrierwave.rb
CarrierWave.configure do |config|
  config.storage = :grid_fs
  
  # Storage access url
  config.grid_fs_access_url = "/upload/grid"
end

步骤3：在模型中设置要存储的文件

#app/models/user.rb
class User
  include Mongoid::Document
  mount_uploader :avatar, AvatarUploader
end

步骤4：创建上传文件的管理器。

#app/uploaders/avatar_uploader
class AvatarUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick

  def store_dir
    "#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  version :thumb do
    process :resize_to_limit => [200, 200]
  end
end

步骤5：创建GridFS控制器。

#app/controllers/gridfs_controller.rb
class GridfsController < ApplicationController

  def serve
    gridfs_path = env["PATH_INFO"].gsub("/upload/grid/", "")
    begin
      gridfs_file = Mongoid::GridFS[gridfs_path]
      self.response_body = gridfs_file.data
      self.content_type = gridfs_file.content_type
    rescue
      self.status = :file_not_found
      self.content_type = 'text/plain'
      self.response_body = ''
    end
  end
end

步骤6：配置路由。

#config/routes.rb
get "/upload/grid/*path" => "gridfs#serve"

现在在视图中使用 user.avatar.url 将得到一个有效文件的路径。