R2Doc began as a desire to to create a format for Ruby and Rails documentation that would be more useful than anything currently available (or at least more useful to me). Specifically, I had a small set of goals:

  • To get rid of the really awful frames
  • To allow easy searching by class or method name
  • To make it easier to scan the lists of methods and attributes
  • To limit line length for easier viewing on wide browsers

As RDoc version 1.0.1 was already packaged as part of the Ruby core and version 2 did not yet appear to be stable when I started, I began by building a template for version 1. As soon as I scratched the surface of RDoc, I became immediately dismayed by what I found. The template format was arcane, and much of the presentation logic I hoped to change was embedded in the generator code. R2Doc quickly evolved into more than just another template. While still in its very early stages of development, R2Doc is a generator that is more easily extended and is very much a second set of thoughts on what a framework for documentation generators could and should be. It is my hope that, more than anything, R2Doc will be a contribution to the dialog about the future directions of RDoc.


RDoc version independent
The R2Doc generator is not limited to a particular version of RDoc. It has been tested to work with version 1.0.1 and 2.3.0. Additional versions will be tested as development progresses.
Support for multiple templates
While others will hopefully find the default template useful, some people will almost certainly have different preferences for the format. The beauty of R2Doc is not in its template, but rather in the facilities it provides for creating templates more easily.
Pushes presentation logic into the template
My biggest gripe with the current version of RDoc is that more attention should be paid to what makes Rails so successful as a web development framework. Part of what really works for Rails is that it makes it easy to build an application using a straight-forward MVC pattern and encourages a clean separation between each of the three components of that architecture. RDoc is made up of parts which correspond to each of those components as well. A generator is a controller; the context objects representing the classes, modules, files, and methods found in the code are models; and a template is a view. R2Doc extends the model classes with methods that provide information about the code being documented without directly generating HTML. This pushes presentation logic into the view, making for cleaner code and more powerful templates.
More powerful capabilities within the templates
Another key to the success of Rails is the large collection of utility methods which are specifically made available for use within views. They make common coding tasks easier to accomplish. R2Doc adds a small collection of utility methods specifically design to facilitate template authoring.
Extensible set of template formats
R2Doc provides an ERB engine for templates by default, but it is not limited to only ERB templates. Much like Rails, the file extension of a template dictates which engine it is written for. Template engines can be added to R2Doc and registered to work with additional extensions. So, engines can easily be added to allow template creation in HAML, XML builder, or nearly anything else you care for.


R2Doc is a standard generator, and, as such, can be specified using the -f or —fmt options with the rdoc command. Its gem will be automatically discovered by version 2 of RDoc, but version 1 is slightly trickier as it relies on the $: variable. To facilitate use, R2Doc provides the r2doc command. It‘s usage is:

  r2doc [options] [names...]     # normal usage
  r2doc [options] --gems gems... # generate docs for installed gems

The first usage sets options for using R2Doc as the generator and passes everything else on to rdoc. The second usage is a specialized form for generating docs for an installed gem using the R2Doc generator. By default r2doc uses whatever version of RDoc is your default, but it includes one additional option, —rdoc-version, which allows you to specify the RDoc version when multiple gems are installed.

Creating Templates

R2Doc searches a registered list of directories for templates. Additional directories may be added by calling TemplateManager.add_template_directory Templates are folders within registered directories. So, the default directory registered by the gem is lib/r2doc/template (relative to the directory where the gem is installed) and the default r2doc template is in the folder named lib/r2doc/template/r2doc.

The generator requires template files for index.html, class.html, file.html, and rdoc.js. All non-template files within the template folder are copied to the output directory unchanged (this is useful for supporting files such as images and stylesheets). The best reference for writing templates are the included template files themselves. Utility methods specific to templates can be found in the R2Doc::TemplateUtil module. It may also be useful to look over the additions to the context objects, which are found in the R2Doc::ContextExtensions, R2Doc::ClassExtensions, and R2Doc::MethodExtensions modules.

Creating New Template Engines

Requirements for template engines are explained in the R2Doc::TemplateManager class. Additional engines can be added by calling TemplateManager.register_engine.