Railsメモ(2) : モデルを作成する

ひな形の作成は完了したので、次に曲のモデルを作成する。
曲の属性としては下記項目を保存することにする。
アーティスト名は別モデルとして作成予定だが、最近の曲はコラボが多いので"featuring"や"and"などを含んだ表示用としてのアーティスト名を保存しておく。

曲名
アーティスト名（表示用）
ランキング
年

Songモデルを作成するために下記コマンドを実行。

$ ./bin/rails g model Song title:string display_artist:string ranking:integer year:integer
      invoke  active_record
      create    db/migrate/20150803142639_create_songs.rb
      create    app/models/song.rb

次にマイグレーションの内容をDBに反映させるために下記コマンドを実行。

$ ./bin/rake db:migrate
== 20150803142639 CreateSongs: migrating ======================================
-- create_table(:songs)
   -> 0.0022s
== 20150803142639 CreateSongs: migrated (0.0023s) =============================

rails consoleを使って試しに3曲のデータを追加してみる。

$ ./bin/rails c
Loading development environment (Rails 4.2.3)
irb(main):001:0> Song.all
  Song Load (1.8ms)  SELECT "songs".* FROM "songs"
=> #<ActiveRecord::Relation []>
irb(main):002:0> Song.create title: 'Happy', display_artist: 'Pharrell Williams', ranking: 1, year: 2014
   (0.1ms)  begin transaction
  SQL (0.4ms)  INSERT INTO "songs" ("title", "display_artist", "ranking", "year", "created_at", "updated_at") VALUES (?, ?, ?, ?, ?, ?)  [["title", "Happy"], ["display_artist", "Pharrell Williams"], ["ranking", 1], ["year", 2014], ["created_at", "2015-08-04 11:34:44.627823"], ["updated_at", "2015-08-04 11:34:44.627823"]]
   (13.9ms)  commit transaction
=> #<Song id: 1, title: "Happy", display_artist: "Pharrell Williams", ranking: 1, year: 2014, created_at: "2015-08-04 11:34:44", updated_at: "2015-08-04 11:34:44">
irb(main):003:0> Song.create title: 'Dark Horse', display_artist: 'Katy Perry featuring Juicy J', ranking: 2, year: 2014
   (0.1ms)  begin transaction
  SQL (0.8ms)  INSERT INTO "songs" ("title", "display_artist", "ranking", "year", "created_at", "updated_at") VALUES (?, ?, ?, ?, ?, ?)  [["title", "Dark Horse"], ["display_artist", "Katy Perry featuring Juicy J"], ["ranking", 2], ["year", 2014], ["created_at", "2015-08-04 11:35:38.032988"], ["updated_at", "2015-08-04 11:35:38.032988"]]
   (12.2ms)  commit transaction
=> #<Song id: 2, title: "Dark Horse", display_artist: "Katy Perry featuring Juicy J", ranking: 2, year: 2014, created_at: "2015-08-04 11:35:38", updated_at: "2015-08-04 11:35:38">
irb(main):004:0> Song.create title: 'All of Me', display_artist: 'John Legend', ranking: 3, year: 2014
   (0.1ms)  begin transaction
  SQL (0.8ms)  INSERT INTO "songs" ("title", "display_artist", "ranking", "year", "created_at", "updated_at") VALUES (?, ?, ?, ?, ?, ?)  [["title", "All of Me"], ["display_artist", "John Legend"], ["ranking", 3], ["year", 2014], ["created_at", "2015-08-04 11:36:15.782787"], ["updated_at", "2015-08-04 11:36:15.782787"]]
   (7.9ms)  commit transaction
=> #<Song id: 3, title: "All of Me", display_artist: "John Legend", ranking: 3, year: 2014, created_at: "2015-08-04 11:36:15", updated_at: "2015-08-04 11:36:15">
irb(main):005:0> Song.all
  Song Load (0.3ms)  SELECT "songs".* FROM "songs"
=> #<ActiveRecord::Relation [#<Song id: 1, title: "Happy", display_artist: "Pharrell Williams", ranking: 1, year: 2014, created_at: "2015-08-04 11:34:44", updated_at: "2015-08-04 11:34:44">, #<Song id: 2, title: "Dark Horse", display_artist: "Katy Perry featuring Juicy J", ranking: 2, year: 2014, created_at: "2015-08-04 11:35:38", updated_at: "2015-08-04 11:35:38">, #<Song id: 3, title: "All of Me", display_artist: "John Legend", ranking: 3, year: 2014, created_at: "2015-08-04 11:36:15", updated_at: "2015-08-04 11:36:15">]>

これで曲のモデルにデータを追加できることを確認したが、
rails consoleが見にくいので次のステップで見やすくしてみる。