Using yri for Ruby Core Classes
This functionality requires a couple of changes made in 0.5.1 (released today), so be sure to update yard to the latest release.
You can now use yri with Ruby core classes. This is relatively old news (as of yesterday) since YARD can now parse core classes, but Ruby source is generally not available on all installs, so building the .yardoc database is not always an option.
In YARD 0.5.1 (released today), instead of downloading and parsing the Ruby source manually, you can now download a pre-built gem containing the .yardoc files for a bunch of Ruby versions (1.8.6, 1.8.7, 1.9.1). Simply use:
$ gem install yard-doc-core
You should now be able to use something like yri String#split. By default this will install docs for 1.9.1, but if you need docs for a specific version of Ruby, add -v VERSION to your gem install command:
$ gem install yard-doc-core -v 1.8.7
The stdlib package (yard-doc-stdlib) will be coming soon.