未定义的方法`all＆＃39; for Imageable：模块

Question

我对rails 4的问题有疑问。我写了一个问题：

module Imageable
  extend ActiveSupport::Concern

  included do
    belongs_to :imageable   
    has_many :images, foreign_key: 'imageable_id', dependent: :destroy
    # has_one :primary_image, ->( limit(1) ), foreign_key: imageable_id, class_name: 'Image'
    accepts_nested_attributes_for :images, reject_if: proc { |attributes| attributes['source'].blank? }, allow_destroy: true
    after_initialize :build_image
 end

 private
  def build_image
    self.build_imageable if self.imageable.present? && self.new_record?
    self.images.build if self.images.blank? && self.new_record?
  end
end

我的私有build_image方法有问题。此方法的第一行引发错误：

undefined method `all' for Imageable:Module

当这个代码在模型内部时，并不关心一切正常。有什么想法吗？