如何添加验证以在Rails应用程序中重新归档？

我创建了Rails应用程序，因此可以使用API​​部分。我可以使用curl成功地将文件上传到rails应用程序的数据库，但是我不知道如何将文件类型/内容类型限制为仅CSV。

csv_file.rb＃模型

class CsvFile < ActiveRecord::Base
    # attachment :content_type => "text/csv"
    # http://ryanbigg.com/2009/04/how-rails-works-2-mime-types-respond_to/
    attachment :csv, extension: "csv", content_type: "text/csv"
end

csv_files.rb＃控制器

class API::V1::CsvFilesController < ApplicationController

  # see http://stackoverflow.com/questions/15040964/ for explanation
  skip_before_filter :verify_authenticity_token

  def index
    @csv_files = CsvFile.all
    if @csv_files
      render json: @csv_files,
        # each_serializer: PictureSerializer,
        root: "csv_files"
    else
      @error = Error.new(text: "404 Not found",
                          status: 404,
                          url: request.url,
                          method: request.method)
      render json: @error.serializer
    end 
  end

  def show
    if @csv_file
      render json: @csv_file,
              # serializer: PictureSerializer,
              root: "csv_file"
    else
      @error = Error.new(text: "404 Not found",
                          status: 404,
                          url: request.url,
                          method: request.method)
      render json: @error.serializer
    end
  end

  # POST /csv_files.json
  def create
    @csv_file = CsvFile.new(csv_params)

    if @csv_file.save
      render json: @csv_file,
        # serializer: PictureSerializer, 
        meta: { status: 201,
          message: "201 Created"},
          root: "csv_file"
    else
      @error = Error.new(text: "500 Server Error",
        status: 500,
        url: request.url,
        method: request.method)
      render :json => @error.serializer
    end
  end

  def update
  end

  def delete
  end

  private

  def csv_params

  end
end