RegExp Before Filter in Sinatra

February 19, 2010

Sinatra doesn’t support arguments to the before filtering method for routing. I wrote a very small method to support this.

I suppose the reason why Sinatra’s before filter is so simple is because most of the time a Siantra app only does 1 very small thing. My apps in Sinatra have been getting more complex but I don’t want to incur all the overhead and boiler plate associated with Rails. RegExp-based filtering is good for keeping your code DRY and adding things like authentication only for specific routes, say ones starting with /admin

Here’s what my little extension looks like:

~~{.ruby} module Sinatra

module RegexpRouteFilter def before_with_regexp(pattern, &blk) before do instance_eval(&blk) if request.path =~ pattern end end end

register RegexpRouteFilter

end

Here’s a sample of how you’d use it in a routes file:

before_with_regexp(/^\/admin/) do
  # call authentication methods here
  halt 401, "GO AWAY!"
end

get '/admin/super_secret' do
  #...
end

get '/admin/do_junk' do
  #...
end