ruby-on-rails - Rails 3 多态关联引发 NameError

Question

我有以下两个模型:

class FuzzyDate < ActiveRecord::Base
  belongs_to :fuzzy_dateable, :polymorphic => true
end

class Device < ActiveRecord::Base
  has_one :received_date, :as => :fuzzy_dateable
end

具有以下架构:

  create_table "devices", :force => true do |t|
    t.string   "meid"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "fuzzy_dates", :force => true do |t|
    t.date     "date"
    t.integer  "fuzz"
    t.integer  "fuzzy_dateable_id"
    t.string   "fuzzy_dateable_type"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

让我们启动控制台，好吗？

>> d = Device.create(:meid => "A")
=> #<Device id: 1, meid: "A", created_at: "2010-12-16 06:52:55", updated_at: "2010-12-16 06:52:55">
>> fd = FuzzyDate.create(:date => Date.today, :fuzz => 3)
=> #<FuzzyDate id: 1, date: "2010-12-15", fuzz: 3, fuzzy_dateable_id: nil, fuzzy_dateable_type: nil, created_at: "2010-12-16 06:53:04", updated_at: "2010-12-16 06:53:04">
>> fd.fuzzy_dateable = d
=> #<Device id: 1, meid: "A", created_at: "2010-12-16 06:52:55", updated_at: "2010-12-16 06:52:55">
>> fd
=> #<FuzzyDate id: 1, date: "2010-12-15", fuzz: 3, fuzzy_dateable_id: 1, fuzzy_dateable_type: "Device", created_at: "2010-12-16 06:53:04", updated_at: "2010-12-16 06:53:04">

好的，到目前为止，还不错。让我们从另一个方向:

>> d.received_date
NameError: uninitialized constant Device::ReceivedDate
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/base.rb:1199:in `compute_type'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/reflection.rb:162:in `send'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/reflection.rb:162:in `klass'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/reflection.rb:198:in `quoted_table_name'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/has_one_association.rb:97:in `construct_sql'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations/has_one_association.rb:7:in `initialize'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations.rb:1450:in `new'
        from /Library/Ruby/Gems/1.8/gems/activerecord-3.0.3/lib/active_record/associations.rb:1450:in `received_date'
        from (irb):5
>> 

呸!我已经做了很多 Googleing，我发现的答案都是错误地使用复数模型名称，这里不是这种情况。我花了几个晚上的时间来反对这个问题，所以非常感谢任何指导。

Answer 1

这里的问题是，在您的 Device 模型中，您将关联命名为 :received_date 并且默认情况下它将查找 ReceivedDate 模型，除非您另有说明。

我会说您可以从这些解决方案中选择任何一种。

没有。 1

class Device < ActiveRecord::Base
  has_one :received_date, :as => :fuzzy_dateable, :class_name => "FuzzyDate"
end

没有。 2

class Device < ActiveRecord::Base
  has_one :fuzzy_date, :as => :fuzzy_dateable
end