Rails 4.1.x HABTM 未定义方法'foreign_key'

Question

以下定义适用于 Rails 4.0.x 及更低版本：

module Gemgento
   class Product < ActiveRecord::Base
      has_and_belongs_to_many :stores, -> { distinct }, join_table: 'gemgento_stores_products', class_name: Gemgento::Store
   end
end

但是，升级到 Rails 4.1.x 后，每当初始化 Gemgento::Product 类时，我都会收到以下错误。

NoMethodError: undefined method `foreign_key' for #<Class:0x007f870f18e668>
from /Users/Kevin/.rvm/gems/ruby-1.9.3-p429@sellect/gems/activerecord-4.1.4/lib/active_record/dynamic_matchers.rb:26:in `method_missing'
from /Users/Kevin/.rvm/gems/ruby-1.9.3-p429@sellect/gems/activerecord-4.1.4/lib/active_record/associations/builder/has_and_belongs_to_many.rb:113:in `belongs_to_options'
from /Users/Kevin/.rvm/gems/ruby-1.9.3-p429@sellect/gems/activerecord-4.1.4/lib/active_record/associations/builder/has_and_belongs_to_many.rb:82:in `through_model'
from /Users/Kevin/.rvm/gems/ruby-1.9.3-p429@sellect/gems/activerecord-4.1.4/lib/active_record/associations.rb:1580:in `has_and_belongs_to_many'
from /Users/Kevin/Sites/gemgento/app/models/gemgento/product.rb:21:in `<class:Product>'

Answer 1

在 Rails 4.1 中搜索任何记录在案的 HABTM 更改后，我找不到任何东西。 4.0 中也没有弃用警告。原来:class_name必须定义为String。

module Gemgento
   class Product < ActiveRecord::Base
      has_and_belongs_to_many :stores, -> { distinct }, join_table: 'gemgento_stores_products', class_name: 'Gemgento::Store'
   end
end

此更改不会影响任何其他关联。但确保从现在开始始终使用字符串可能是件好事。