Things I Didn't Know Rails Could Do

Something I thing it's easy and useful to me from James Edward Gray II presentation in RailsConf 2012
Ten Things You Didn't Know Rails Could Do

• rails c --sandbox
• rake db:migrate:status
• pluck
• User.pluck(:email)
• User.uniq.pluck(:email)
• Count Record in Group
• Model.group(:column).count
• File.atomic_write
• { nested: { a: 1 } }.deep_merge(nested: { b: 2 })
• hash.except(:key1, :key2)
• hash1.reverse_merge(hash2) # keep hash1 value if hash2 has a duplicate key
• content_tag_for(:tag, array) { |e| # content_inside }
• render partial: @active_record_model & to_partial_path
• grouped_options_for_select