Question

I get the following error when trying to run the most basic Cloudkit example, as shown here http://getcloudkit.com/curl.html:

 /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/cloudkit-0.11.2/lib/cloudkit/rack/builder.rb:43
 :in `expose': undefined method `<<' for nil:NilClass (NoMethodError)   
 from /Users/ed/Work/Play/config.ru:3:in `block in <main>'

from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/builder.rb:51:in `instance_eval'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/builder.rb:51:in `initialize'
from /Users/ed/Work/Play/config.ru:1:in `new'
from /Users/ed/Work/Play/config.ru:1:in `<main>'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/builder.rb:40:in `eval'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/builder.rb:40:in `parse_file'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/server.rb:200:in `app'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/server.rb:301:in `wrapped_app'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/server.rb:252:in `start'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/lib/rack/server.rb:137:in `start'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/gems/rack-1.4.1/bin/rackup:4:in `<top (required)>'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/bin/rackup:19:in `load'
from /Users/ed/.rvm/gems/ruby-1.9.2-p180/bin/rackup:19:in `<main>'

Any ideas what this could be?

Answer 1

You probably have a version of Rack installed which is greater than 1.4
CloudKit is not Rack 1.4 ready.

Quick fix

$ gem uninstall -v '>=1.4' rack
$ gem install rack -v 1.3.6

Update:

Another solution is to specify which version of rack to load by not using rackup but this inline command:

$ gem install rack -v 1.3.6
$ ruby -e "gem 'rack', '=1.3.6'; require 'rack'; Rack::Server.start" config.ru