通过具有范围的关联保存时丢失属性（Rails 4.0.0）

代码（Rails 4.0.0）

class Track  { where(:artist_tracks => { :artistic_role_id => 1 }) }, :through => :artist_tracks, :source => :artist end class ArtistTrack < ActiveRecord::Base belongs_to :artist belongs_to :track belongs_to :artistic_role end class Artist  :artist_tracks end 

寻找作品

 # artist_tracks.artistic_role_id is properly set to "1" 2.0.0p195 :003 > Track.last.owning_artists Track Load (1.1ms) SELECT "tracks".* FROM "tracks" ORDER BY "tracks"."id" DESC LIMIT 1 Artist Load (0.8ms) SELECT "artists".* FROM "artists" INNER JOIN "artist_tracks" ON "artists"."id" = "artist_tracks"."artist_id" WHERE "artist_tracks"."artistic_role_id" = 1 AND "artist_tracks"."track_id" = $1 [["track_id", 10]] 

创建不起作用

 # artist_tracks.artistic_role_id is totally missing from the INSERT 2.0.0p195 :005 > Track.create!(name: "test_name", lyrics: "test_lyrics", owning_artist_ids: [1]) Artist Load (1.3ms) SELECT "artists".* FROM "artists" WHERE "artists"."id" = $1 LIMIT 1 [["id", 1]] (0.5ms) BEGIN Artist Exists (0.7ms) SELECT 1 AS one FROM "artists" WHERE ("artists"."name" = 'TestArtist1' AND "artists"."id" != 1) LIMIT 1 SQL (0.7ms) INSERT INTO "tracks" ("created_at", "lyrics", "name", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["created_at", Thu, 13 Jun 2013 22:20:14 UTC +00:00], ["lyrics", "test_lyrics"], ["name", "test_name"], ["updated_at", Thu, 13 Jun 2013 22:20:14 UTC +00:00]] # # YU NO have artist_tracks.artistic_role_id? # SQL (0.7ms) INSERT INTO "artist_tracks" ("artist_id", "created_at", "track_id", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["artist_id", 1], ["created_at", Thu, 13 Jun 2013 22:20:14 UTC +00:00], ["track_id", 12], ["updated_at", Thu, 13 Jun 2013 22:20:14 UTC +00:00]] (1.0ms) COMMIT 

根据Rails热门记录协会指南（4.3.3.1在哪里） ，我相信我对范围和期望的使用是有效的：

如果您使用散列样式where选项，则通过此关联创建的记录将使用散列自动确定范围。

为什么artist_tracks.artistic_role_id属性丢失了？ 如果我的期望是错误的，我想了解为什么以及如何实施替代解决方案。

我还在Rails repo上列出了这个问题 。 任何见解都表示赞赏！ 谢谢

Answer 1

我相信发生的事情是，这里实际创建的关联模型是连接模型， artist_tracks ，而不是与其实际条件的关联。 您可以通过声明与条件的备用连接关联，然后通过它附加owning_artists来解决此问题。 像这样：

 class Track < ActiveRecord::Base has_many :artist_tracks has_many :owning_artist_tracks, -> { where(:artistic_role_id => 1) }, :class_name => "ArtistTrack" has_many :owning_artists, :through => :owning_artist_tracks, :source => :artist end