ruby-on-rails - 通过...处理 has_many 的 rails 中的关联...但是两个连接表很深

Question

编辑 4. 我的解释中有些地方不对...附上一张(做得很差的图形)，它显示了表格和模式，然后我的主要问题是我有什么供应商通过 provider_location 表通过组位置 ID 加入，组位置包含组，最后是组名。这就是我想知道的，建一个这样的表如何获取组名？一直来自供应商。这就像我需要一个 has_many 通过。 (重要提示:图中的 Provider Address 和 Group Address 实际上是 Provider Location 和 Group Location)

编辑 x 3:谢谢@mrshoco。它让我更接近了，现在它就像我的结构不太正确的其他东西......我在运行 provider_test_location.rb 时收到此错误

vagrant@precise32:/vagrant/ipanmv2$ rake test test/models/provider_location_tes
t.rb
Run options: --seed 18117

# Running:

E

Finished in 0.190900s, 5.2383 runs/s, 5.2383 assertions/s.

  1) Error:
ProviderLocationTest#test_fetching_a_group_name_for_a_provider:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: provider_
locations.group_id: SELECT groups.group_name FROM "groups" INNER JOIN "provider_
locations" ON "provider_locations"."group_id" = "groups"."id" INNER JOIN "provid
ers" ON "providers"."id" = "provider_locations"."provider_id" WHERE "providers".
"first_name" = 'Shane'
    test/models/provider_location_test.rb:37:in `puts'
    test/models/provider_location_test.rb:37:in `puts'
    test/models/provider_location_test.rb:37:in `block in <class:ProviderLocatio
nTest>'

1 runs, 1 assertions, 0 failures, 1 errors, 0 skips

这是完整的单元测试

require 'test_helper'

class ProviderLocationTest < ActiveSupport::TestCase
  # test "the truth" do
  #   assert true
  # end

   test "adding a provider to a group location" do
    group = Group.new
    group.group_name = 'My Awesome'
    group.save
    adr = Address.new
    adr.city = 'Las Cruces'
    adr.state = 'New Mexico'
    adr.zip = '88012'
    adr.address_line_one = '382 Dark side of moon'
    adr.address_line_two = ''
    adr.save    

    gl  = GroupLocation.new
    gl.group = group
    gl.address=adr      
    gl.save


    prv = Provider.new
    prv.first_name = 'Shane'
    prv.last_name = 'Thomas'
    prv.save

    pl = ProviderLocation.new      
    pl.provider = prv
    pl.group_location = gl   ###############ISSUE

    assert pl.save, 'Provider location did not save'

    puts Group.joins(:providers).where(providers: { first_name: 'Shane' }).select('groups.group_name')




  end
end

模型如下:

class Provider < ActiveRecord::Base
    belongs_to :designation
    belongs_to :specialty
    has_many :provider_locations
    has_many :invoices
    has_many :groups, through: :provider_locations
end

class ProviderLocation < ActiveRecord::Base
  belongs_to :provider
  belongs_to :group_location
end

class Group < ActiveRecord::Base

    #validations
    validates :group_name, presence: true


    #associations
    has_many :providers, through: :provider_locations
    has_many :invoices
    has_one  :billing
    has_many :addresses, through: :group_locations


    has_many :group_locations
    belongs_to  :billing_address, class_name: 'Address', foreign_key: 'billing_address_id'
    belongs_to  :mailing_address, class_name: 'Address', foreign_key: 'mailing_address_id'
    has_and_belongs_to_many :insurances
    has_many :provider_locations



end


class GroupLocation < ActiveRecord::Base
  belongs_to :address
  belongs_to :group

end

class Address < ActiveRecord::Base
    has_many :group_locations
    has_many :billings
end

Answer 1

# Group name given a provider name
Group.joins(:providers).where('providers.first_name' => 'Shane').select('groups.name')

# address/location of the provider given the group name
Provider.joins(:groups).where("groups.name" => "your_group_name").first.provider_locations.first