运行 Rails 3.2.1。如文档(http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association)所示,通过关联尝试应该是简单的嵌套 has_many:
class Company < ActiveRecord::Base
has_many :locations, :dependent => :destroy
has_many :assets, :through => :locations
has_many :components, :through => :assets
end
class Location < ActiveRecord::Base
belongs_to :company
has_many :assets
has_many :components, :through => :assets
end
class Asset < ActiveRecord::Base
belongs_to :location
has_many :components
end
class Component < ActiveRecord::Base
belongs_to :asset
end
在控制台中Company.find(2)
工作正常,Company.find(2).locations
但不是Company.find(2).assets
or Company.find(2).components
。我得到:
1.9.3p0 :071 > Company.find(2).assets
Company Load (0.8ms) SELECT "companies".* FROM "companies" WHERE "companies"."id" = $1 ORDER BY name ASC LIMIT 1 [["id", 2]]
NoMethodError: undefined method `assets' for #<Company:0x007f939d714318>
我似乎在这里遗漏了一些东西。我嵌套了一层更深,但根据文档,这应该没问题。