ruby使用carrierwave上传附件

使用carrierwave插件保存附件：
创建attachments多态表来实现附件的存储关联。

gem 'carrierwave'

migration

class CreateAttachments < ActiveRecord::Migration[5.0]
  def change
    create_table :attachments do |t|
      t.string :attachment_entity_type, limit: 64
      t.integer :attachment_entity_id
      t.string :path, comment: '文件类容'
      t.string :name, comment: '文件名'
      t.string :content_type, comment: '文件类型'
      t.integer :file_size, comment: '文件大小'
      t.integer :created_by, comment: '上传人'
      t.timestamps
    end
  end
end

create_table "blogs", force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8" do |t|
    t.string "title"
    t.text "content"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "cover_img", comment: "封面"
    t.integer "category_id", comment: "类型"
    t.integer "view_count", comment: "文章访问次数"
    t.integer "seq", default: 10, comment: "顺序"
end

model

class Attachment < ApplicationRecord
  #定义多态
  belongs_to :attachment_entity, polymorphic: true, optional: true
  #继承CarrierWave方法
  mount_uploader :path,  AttachmentUploader
  before_save :set_fields

  def set_fields
    self.content_type = path.content_type
    self.file_size = path.size
    self.name = path.get_original_filename
  end

  def delete_company_attachment_it
    self.destroy
    true
  end

  def attachment_path
    path.url
  end

end


class Blog < ApplicationRecord
  # 关联多态
  has_many :attachments, as: :attachment_entity
  belongs_to :category, optional: true
  has_many :comments

	def user_name
      "@#{self.title}"
	end

	def self.view_count_top
      order(view_count: :desc).limit(5)
	end

	def cover_img_path
  	  self.cover_img ? Attachment.find(self.cover_img.to_i).path.url : "/assets/f10.jpg"
  end

end

AttachmentUploader

class AttachmentUploader < CarrierWave::Uploader::Base
   def store_dir
    "uploads/#{model.attachment_entity_type.to_s.underscore}/#{mounted_as}/#{model.id}"
  end
end

controller

def create
    @blog = Blog.new(blog_params)
    attachment = Attachment.create(attachment_entity_type: "Blog",attachment_entity_id: @blog.id , path: params[:draft_img], created_by: 1 ) 
     @blog.cover_img = attachment.id
     @blog.save
end

view

<%= form_for @blog, url: url, method: meth, :html => { :multipart => true } do |f| %>
  <div class="field">
    <%= file_field_tag "draft_img", id: 'draft_img' %>
    <%= f.text_field :title, class: 'form-control input-sm', style: 'width: 280px;' %>
    <%= text_area_tag 'blog[content]', @blog.content %>
  </div>
  <%= f.submit :class=>"ui primary button"%>
<% end %>