在Rails的4.0.4本code的工作：

in Rails 4.0.4 this code work:

mailboxes = Mailbox.order(:mailbox)
mailboxes.keep_if do |mailbox|
  # test
end

在Rails的4.1.0用 NoMethodError突破（未定义的方法keep_if为＆LT;邮箱:: ActiveRecord_Relation：0x5494f80＆GT;）

in Rails 4.1.0 it break with NoMethodError (undefined method keep_if for <Mailbox::ActiveRecord_Relation:0x5494f80>)

和已被改变，以

mailboxes = Mailbox.order(:mailbox).to_a
mailboxes.keep_if do |mailbox|
  # test
end

我没有找到有关的任何信息。

I don't find any information about that

你知道吗？

推荐答案

及其release说明钢轨4.1

关联不再具有突变的方法，如#map！和#delete_if。   通过调用#to_a使用这些方法之前转换成一个阵列。 （拉   请求）

Relation no longer has mutator methods like #map! and #delete_if. Convert to an Array by calling #to_a before using these methods. (Pull Request)

由于 keep_if 是一个赋值函数方法，它从关联删除

Since keep_if is a mutator method, its removed from Relation