Simple, dynamic and efficient activerecord model constants.
Ever wanted to be able to be able to do something like:
case buoy.buoy_type when BuoyType::NOAA .. when BuoyType::SCRIPPS .. end
Bouy.create(:name => :foo, :bouy_type => BuoyType::NOAA)
but weren't sure the best / most efficient way to implement?
One way would be to do something like:
class BuoyType < ActiveRecord::Base NOAA = find_by_name('noaa') .. end
However, this approach can become tedious and tough to manage.
Another way would be to dynamically create the constants for all the rows in the given table at rails start. However, for models w/hundreds of rows, e.g., Country, City, this wouldn't be very efficient either.
This gem minimizes the db calls by memoizing the finder that is used to look up the constant values. So, it depends on your app server but only the first refernece to a given constant should require a db query (see the code and specs for more details).
Standard gem install:
gem install constantize
After installing the gem you would need to require it:
Rails 2.x / No Bundler
In a Rails 2.x project you can add this to your environment.rb:
Rails 3.x / Bundler
In Rails 3.x add this to your Gemfile:
In the model that you will be "constantizing" simply add the following to the top:
where :key is the name of the field that will be used to build the finder.
class BuoyType < ActiveRecord::Base constantize :name .. end
this would assume that your buoy_types table looked something like:
+----+---------+ | id | name | +----+---------+ | 1 | noaa | | .. | +----+---------+
if your table used a different field, say :title, rather than :name:
+----+---------+ | id | title | +----+---------+ | 1 | noaa | | .. | +----+---------+
then your model definition would look like:
class BuoyType < ActiveRecord::Base constantize :title .. end
Finally, if you wanted only the :id to be returned from the constant call (rather than the entire model) you could do:
class BuoyType < ActiveRecord::Base constantize :name, :id .. end
and your call to BuoyType::NOAA would return only the interger :id value (1 in this case).
Note on Patches/Pull Requests
- Fork the project.
- Make your feature addition or bug fix.
- Add tests for it. This is important so I don't break it in a future version unintentionally.
- Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
- Send me a pull request. Bonus points for topic branches.
Copyright (c) 2010 Adam Weller. See LICENSE for details.