fohow_admin/app/models/product_picture.rb

require 'uuid'
class ProductPicture < ActiveRecord::Base
    has_paper_trail
    self.table_name = "product_pictures"
    after_destroy :after_destroy
    belongs_to :product
    validates :product_id, presence: true
    attr_accessor :v_img

    IMG_STORE_PATH = "product_pictures" 

    PIC_TYPE_ENUM = [["详情图",1],["轮播图",0]]

    rails_admin do
        navigation_label '商品管理'
        weight -240

        list do
            filters [:id,:pic_type]
            field :id
            field :product
            field :img do
                formatted_value do
                    bindings[:view].tag(:img,{:src => bindings[:object].get_img,
                        :style => 'width: 100px;height: 100px;cursor: pointer;display: block;max-width: 100px;',
                        :onClick => "javascript:window.open('#{bindings[:object].get_img}')"})
                end
            end
            field :pic_type,:enum do
                enum do
                    PIC_TYPE_ENUM
                end
            end
            field :sort
            field :created_at
            field :updated_at
        end

        show do
            field :id
            field :product
            field :img do
                formatted_value do
                    bindings[:view].tag(:img,{:src => bindings[:object].get_img,
                    :style => 'width: 100px;height: 100px;cursor: pointer;display: block;max-width: 100px;',
                    :onClick => "javascript:window.open('#{bindings[:object].get_img}')"})
                end
            end
            field :pic_type, :enum do
                enum do
                    PIC_TYPE_ENUM
                end
            end
            field :sort
            field :created_at
            field :updated_at
        end

        edit do
            field :product
            field :v_img, :file_upload do
                pretty_value do
                    bindings[:view].tag(:img,{:src => bindings[:object].get_img, :class => 'preview'})
                end
            end
            field :pic_type,:enum do
                enum do
                    PIC_TYPE_ENUM
                end
            end
            field :sort
        end

    end

    def v_img=file
        unless file.blank?
            # clear_img
            file_name = "#{UUID.new.generate[0...8].downcase}.jpg"
            file_path = "#{IMG_STORE_PATH}/#{file_name}"
            Ali::Oss.store(Ali::Oss::BUCKET_NAME_PUBLIC_READ, file_path, file.read)
            self.img = file_path
            self.save
        end
    end


    def clear_img
        file_path = "#{self.img}"
        Ali::Oss.delete_object(Ali::Oss::BUCKET_NAME_PUBLIC_READ,file_path)
    end

    def get_img
        url = "http://#{Ali::Oss::CDN_URL_FOR_HOST}/#{self.img}"
        return url
    end

    def after_destroy
        clear_img
    end
end