has_many through sql - ruby-on-rails-3

Question

Well my models are User, Exercise and Writing.
class User < ActiveRecord::Base
has_many :exercises, :through => :writings
has_many :writings
end
class Exercise < ActiveRecord::Base
has_many :users, :through => :writings
has_many :writings
end
class Writing < ActiveRecord::Base
belongs_to :user
belongs_to :exercise
attr_accessible :writing_date, :exercise_id
end
my db/schema.rb
ActiveRecord::Schema.define(:version => 20120517142448) do
create_table "exercises", :force => true do |t|
t.string "etitle"
t.text "ebody"
t.decimal "average", :precision => 3, :scale => 1
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "users", :force => true do |t|
t.string "email", :default => "", :null => false
t.datetime "created_at"
t.datetime "updated_at"
t.integer "user_kind", :default => 0
end
create_table "writings", :force => true do |t|
t.integer "user_id"
t.integer "exercise_id"
t.date "writing_date"
t.datetime "created_at"
t.datetime "updated_at"
end
the join table is Writing. I try to show on exercise view (app/view/exercises/index.html.erb) for each exercise_id her writing_date. Each user_id has many exercise_id through Writing table. Each record on Writing table has writing_id, user_id, exercise_id and writing_date. In console for specifically exercise_id I made it like this:
1.9.2p290 :001 > #exercise = Exercise.find_by_id(9)
=> #<Exercise id: 9, etitle: "PLS51-2012-E01", ebody: "q", average: #<BigDecimal:53eeba8,'0.1E2',9(18)>, created_at: "2012-05-20 14:31:07", updated_at: "2012-05-20 14:34:27", askisi_file_name: nil, askisi_content_type: nil, askisi_file_size: nil, askisi_updated_at: nil>
1.9.2p290 :002 > #exercise.writings
=> [#<Writing id: 6, user_id: 1, exercise_id: 9, writing_date: "2012-06-29", created_at: "2012-05-20 14:36:45", updated_at: "2012-05-20 14:36:45">, #<Writing id: 12, user_id: 7, exercise_id: 9, writing_date: "2012-06-20", created_at: "2012-05-20 14:40:12", updated_at: "2012-05-20 14:40:12">, #<Writing id: 13, user_id: 7, exercise_id: 9, writing_date: "2012-05-02", created_at: "2012-05-20 15:41:54", updated_at: "2012-05-20 15:41:54">]
1.9.2p290 :003 > #exercise.writings.order("writing_date ASC")
=> [#<Writing id: 13, user_id: 7, exercise_id: 9, writing_date: "2012-05-02", created_at: "2012-05-20 15:41:54", updated_at: "2012-05-20 15:41:54">, #<Writing id: 12, user_id: 7, exercise_id: 9, writing_date: "2012-06-20", created_at: "2012-05-20 14:40:12", updated_at: "2012-05-20 14:40:12">, #<Writing id: 6, user_id: 1, exercise_id: 9, writing_date: "2012-06-29", created_at: "2012-05-20 14:36:45", updated_at: "2012-05-20 14:36:45">]
1.9.2p290 :004 > #exercise.writings.order("writing_date ASC").last
=> #<Writing id: 6, user_id: 1, exercise_id: 9, writing_date: "2012-06-29", created_at: "2012-05-20 14:36:45", updated_at: "2012-05-20 14:36:45">
Do I need scope?
Thanks in advance!

Answer 1

Finaly the solution for my problem that can help someone with the same situation is simple. File app/view/exercises/index.html.erb
Code:
<%= exercise.writings.last.try(:writing_date) %>