Question

我有一些像这样的模型类：

class Organisation < ActiveRecord::Base
  has_many :dongles
  has_many :licences_on_owned_dongles, :through => :dongles, :source => :licences,
           :include => [:organisation, :user, :owner_organisation, :profile, :dongle,
                        {:nested_licences => [:profile]} ]
end

class Dongle < ActiveRecord::Base
  has_many :licences
  belongs_to :organisation
end

class Licence < ActiveRecord::Base
  belongs_to :dongle

  # tree-like structure. I don't remember why this had to be done but the comment says
  # "find a way to make the simpler way work again" and I tried using the simpler way
  # but tests still fail. So obviously the SQL awfulness is necessary...
  default_scope :conditions => { :parent_licence_id, nil }
  has_many :nested_licences, :class_name => 'Licence', :dependent => :destroy,
           :autosave => true,
           :foreign_key => :parent_licence_id,
           :finder_sql => proc {
             "SELECT l.* FROM licences l WHERE l.parent_licence_id = #{id}" },
          :counter_sql => proc {
             "SELECT COUNT(*) FROM licences l WHERE l.parent_licence_id = #{id}" }
end

现在我可以这样做：

test "getting licences on owned dongles" do
  org = organisations(:some_other_corp)
  assert_equal [licences(:licence_4)], org.licences_on_owned_dongles
end

幸福地过去了。既然它是一个关联，你可以find()就可以了：

test "getting licences on owned dongles and then filtering further" do
  org = organisations(:some_other_corp)
  conditions = { :owner_organisation_id => nil }
  assert_equal [licences(:licence_4)],
    org.licences_on_owned_dongles.find(:all, :conditions => conditions)
end

但是这给了：

ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: dongles.organisation_id: SELECT "licences".* FROM "licences" WHERE "licences"."parent_licence_id" IS NULL AND (("dongles".organisation_id = 72179513)) AND ("licences".parent_licence_id = 747059259)
test/unit/organisation_test.rb:123:in `test_getting_licences_on_owned_dongles_and_then_filtering_further'

事实上，当你打电话都是find(:all)时，甚至会发生这种情况。它不仅仅是SQLite，因为我在MySQL的生产（oops）中注意到了这一点。

所以我不知道。进一步调查真的太神秘了。我可能会把它搁置为“Rails就不能在一个关联上找到（）”，使用一个块来过滤它并将其留在那里。但我想把它说出来，以防万一有更好的选择。

（实际上，如果你看一下Rails正在生成的查询，那就完全是胡说八道。不知怎的，它最终生成了一个查询，其中某些东西必须是NULL并且同时等于一个值。即使查询有效，这将返回0行。）

Answer 1

不要在Rails 3应用程序中使用find。

org.licences_on_owned_dongles.find(:all, :conditions => conditions)

应该是

org.licences_on_owned_dongles.where(conditions)

修改：阅读here。

Answer 2

我认为你正在寻找.where：

org.licenses_on_owned_dongles.where(conditions)

在has_many上找到（：all）：通过根本不工作？

2 个答案: