Ducklink is a ruby gem I created to manipulate URLs according to a set of rules.

Rules are expressed in a custom DSL which aims to make the intention very clear.

In the example above, a template is provided to a fictional affiliate provider, affiliate.example.com. The template function defines three custom variables, reference, url and campaign.

The only privileged parameter is url, which corresponds to the original url supplied to Ducklink. Other parameters are simply tokens which correspond to symbols passed to set inside the host blocks. Because host blocks list the hosts to which they apply, parameters can be defined on a per-host basis (the difference between ‘campaign1’ and ‘campaign2’ in the example above).

Host blocks accept a context argument which is a hash of values passed to Ducklink at runtime. Runtime configuration allows completely unique URLs to be generated on the fly for analytics or tracking.