database.ymlをDRYに！

美しくないdatabase.yml

冗長な部分が多い…

development:
  database: db_development
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432
test:
  database: db_development
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432
staging:
  database: db_development
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432
production:
  database: db_production
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432

DRY!

YAMLには、アンカーとエイリアスがあったので書き直してみる

common: &common
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: <%= ENV['DB_PASSWORD'] %>
  port: 5432

development: &development
  database: db_development
  <<: *common

test: *development

staging: *development

production:
  database: db_production
  <<: *common

確認方法

% ruby -r yaml -e 'print YAML.load(ARGF.read()).delete_if {|key| key == "common"}.to_yaml' ./database.yml

こんな感じで、大体あってることが確認できる

---
development: &1
  database: db_development
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432
test: *1
staging: *1
production:
  database: db_production
  adapter: postgresql
  encoding: unicode
  pool: 5
  username: dbuser
  password: "<%= ENV['DB_PASSWORD'] %>"
  port: 5432

参考サイト

プログラマーのための YAML 入門 (初級編) アンカーとエイリアス