ruby-on-rails - ActiveRecord :inverse_of does not work on has_many :through on the join model on create

Question

我无法在创建时让inverse_of在连接模型上工作。我不确定这是一个错误还是只是没有实现。我有以下模型:

class Challenge < ActiveRecord::Base
  has_many :groups, :through => :group_challenges
  has_many :group_challenges, :inverse_of => :challenge

  attr_accessor :contact_ids
end

class GroupChallenge < ActiveRecord::Base
  belongs_to :challenge, :inverse_of => :group_challenges
  belongs_to :group, :inverse_of => :group_challenges

  before_save :check_challenge

  def check_challenge
    Rails.logger.debug("challenge.contact_ids: #{challenge.contact_ids}")
  end
end

class Group < ActiveRecord::Base
  has_many :challenges, :through => :group_challenges
  has_many :group_challenges, :inverse_of => :group
end

contact_ids是 challenge的虚拟属性，创建关联后，我想在 group_challenges模型中访问这些属性。我无法正常工作。这是一个例子:

challenge = Challenge.new :groups => Group.all, :contact_ids => [1,2,3]
# log output => challenge.contact_ids: []

但是，当重新加载模型时， inverse_of可以工作

challenge.reload
challenge.group_challenges.first.challenge.contact_ids
# log output => challenge.contact_ids: [1,2,3]

有谁知道这仅仅是inverse_of的设计限制还是实现中的错误？

Answer 1

按照active record api 3.2.1:“当前:inverse_of支持has_one和has_many(但不支持:through变体)关联。它还为反向为has_one而不是多态的belongs_to关联提供反向支持。”