Rails5では以下のように書ける。 ActiveRecord::Type::Boolean.new.cast(0) # false ActiveRecord::Type::Boolean.new.cast(1) # true ActiveRecord::Type::Boolean.new.cast('0') # false ActiveRecord::Type::Boolean.new.cast('1') # true ActiveRecord::Type::Boolean.new.cast(false) # false ActiveRecord::Type::Boolean.new.cast(true) # true ActiveRecord::Type::Boolean.new.cast('false') # false ActiveRecord::Type::Boolean.new