has_many :through - Self-referential has_many :through associations

Update: This article is now superceded by a new version that is updated for Rails 2.0 changes. Here we go. Rick Olson helped me figure out how to do bi-directional, self-referential associations using has_many :through. It's not obvious (until you know the trick), so here's how it's done. This example is for modeling digraphs. create_table "nodes" do |t| t.column "name", :string t.column "capacity

[a2ikm]

自己参照するhas_many

[ono_matope]

多対多の自己参照結合。 has_many :through

[komagata]

関連テーブルが値を持つ自己参照する多対多をhas_many :throughで対処する。相当きれい。

[mrkn]

ActiveRecord で有効グラフを表現する方法

[june29]

自己参照の多対多表現をhas_many :throughで．例は一般的な有向グラフの表現