Rails Grape API versioning

Question

I am trying to create a skeleton for a REST API using Rails 4.0.4 and Grape 0.7.0 to behave like this:

Calling the API with a specific version:

$ curl -H Accept=application/vnd.acme-v1+json http://localhost:3000/api/a
“a-v1”
$ curl -H Accept=application/vnd.acme-v1+json http://localhost:3000/api/b
“b-v1”

Calling the API with as default:

$ curl http://localhost:3000/api/a
“a-v2”
$ curl http://localhost:3000/api/b
“b-v1”
$ curl http://localhost:3000/api/c
“c-v2”

I have been trying but I couldn't get the desired behavior. I ended up with the following files in my rails app:

app/api/api.rb

require 'grape'
require 'api_v1.rb'
require 'api_v2.rb'

module API
  class Base < Grape::API
    mount API::V2
    mount API::V1
  end
end

app/api/api_v1.rb

require 'grape'

module API
  class V1 < Grape::API
    version 'v1', using: :header, vendor: 'acme', format: :json
    prefix 'api'
    format :json
    get :a do
      "a-v1"
    end
    get :b do
      "b-v1"
    end
  end
end

app/api/api_v2.rb

require 'grape'

module API
  class V2 < Grape::API
    version ['v2', 'v1'], using: :header, vendor: 'acme', cascade: true
    prefix 'api'
    format :json
    get :a do
      "a-v2"
    end
    get :c do
      "c-v2"
    end
  end
end

app/config/routes.rb

...
mount API::Base => '/'
...

With above files I just get the default behavior, no matter which version I specify in the curl command.-

Answer 1

Grape does not (to my knowledge) allow an API class to specify an array of version strings, but I don't think you need to do that here anyway. Also, your curl syntax is incorrect.

Your code works for me once I change the version line in app/api/api_v2.rb to

version 'v2', using: :header, vendor: 'acme', cascade: true

and invoke curl using the correct syntax for the -H parameter (note the colon in place of the equals sign):

$ curl -H Accept:application/vnd.acme-v1+json http://localhost:3000/api/a
"a-v1"
$ curl -H Accept:application/vnd.acme-v1+json http://localhost:3000/api/b
"b-v1"
$ curl http://localhost:3000/api/a
"a-v2"
$ curl http://localhost:3000/api/b
"b-v1"
$ curl http://localhost:3000/api/c
"c-v2"