diff options
| -rw-r--r-- | activerecord/lib/active_record/enum.rb | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb index 5fcc0382d8..34c17f11a9 100644 --- a/activerecord/lib/active_record/enum.rb +++ b/activerecord/lib/active_record/enum.rb @@ -26,12 +26,23 @@ module ActiveRecord # # Good practice is to let the first declared status be the default. # - # Finally, it's also possible to explicitly map the relation between attribute and database integer: + # Finally, it's also possible to explicitly map the relation between attribute and + # database integer with a +Hash+: # # class Conversation < ActiveRecord::Base # enum status: { active: 0, archived: 1 } # end # + # Note that when an +Array+ is used, the implicit mapping from the values to database + # integers is derived from the order the values appear in the array. In the example, + # <tt>:active</tt> is mapped to +0+ as it's the first elemet, and <tt>:archived</tt> + # is mapped to +1+. In general, the +i+-th element is mapped to <tt>i-1</tt> in the + # database. + # + # Therefore, once a value is added to the enum array, its position in the array must + # be maintained, and new values should only be added to the end of the array. To + # remove unused values, the explicit +Hash+ syntax should be used. + # # In rare circumstances you might need to access the mapping directly. # The mappings are exposed through a constant with the attributes name: # |