RDoc is the documentation generator distributed with Ruby. It automatically extracts documentation from source files in Ruby, C, C++, and Fortran. But it doesn’t read Objective-C. Here’s a quick hack to make it do so.

First, find the rdoc/parsers/parse_c.rb file on your system. Mine’s in /usr/lib/ruby. Then edit it, and search for a line like this:

    parse_files_matching(/\.(c|cc|cpp|CC)$/)

Add “m”, the Objective-C extension, to the regular expression. I also added “mm” for Objective-C++.

    parse_files_matching(/\.(m|mm|c|cc|cpp|CC)$/)

That was quick and easy, but it felt a bit dirty to hack the Ruby distribution. Does anyone have time to work out a better way? How about a patch for Ruby?

UPDATE: Here’s a patch script that I used to fix a fresh Leopard installation. It should also work on older systems.

#!/bin/sh
patch /usr/lib/ruby/1.8/rdoc/parsers/parse_c.rb <<END
170c170
<     parse_files_matching(/\.(c|cc|cpp|CC)$/)
---
>     parse_files_matching(/\.(c|cc|cpp|CC|m|mm)$/)
END