In the Wild

To underscore the idea that a little bit of module goes a long way, consider DataMapper. DataMapper is a database interface library similar to ActiveRecord. In about 7,500 lines of pretty heavy-duty code, the core of DataMapper uses primarily a three- and occasionally four-level module hierarchy. If DataMapper can limit itself to a very shallow, manageable module structure and still talk to MYSQL, Postgres, and SQLite, chances are pretty good that a modest handful of modules will work for your project too.

In fact, of the larger Ruby projects that do encase themselves in modules, most manage to fit everything very comfortably into a very small number of modules. The code that reads YAML, everyone’s favorite XML alternative, consists of exactly four modules, with the vast bulk of the code living right in the YAML module. The URI code that comes with Ruby weighs in at about 2,500 lines of code and consists of a grand total of five modules, again with most of the code concentrated in a single module. Finally, we have RubyGems, all of 14,000 lines and just over a dozen modules.