A Grape API mounted on Rack with two versions where v2 builds incrementally on top of v1. In this example the only_in_v1 method is only implemented on version v1, the root method is implemented on both versions, etc.
$ bundle install
$ rackup
# without a version
curl http://localhost:9292/
{"version":"v2"}
curl http://localhost:9292/only_in_v1
{"only_in_v1":"true"}
curl http://localhost:9292/in_both_v1_and_v2
{"in_both_v1_and_v2":"v2"}
# version v2 (current)
Implemented in v2.
curl http://localhost:9292 -H "Accept:application/vnd.acme-v2+json"
{"version":"v2"}
Implemented in v1 and inherited by v2.
curl http://localhost:9292/only_in_v1 -H "Accept:application/vnd.acme-v2+json"
{"only_in_v1":"true"}
Implemented in v2.
curl http://localhost:9292/only_in_v2 -H "Accept:application/vnd.acme-v2+json"
{"only_in_v2":"true"}
curl http://localhost:9292/in_both_v1_and_v2 -H "Accept:application/vnd.acme-v2+json"
{"in_both_v1_and_v2":"v2"}
# version v1 (old)
curl http://localhost:9292 -H "Accept:application/vnd.acme-v1+json"
{"version":"v1"}
curl http://localhost:9292/only_in_v1 -H "Accept:application/vnd.acme-v1+json"
{"only_in_v1":"true"}
curl http://localhost:9292/in_both_v1_and_v2 -H "Accept:application/vnd.acme-v1+json"
{"in_both_v1_and_v2":"v1"}