Rails and Air

As I said last time I've started playing around with Adobe Air, what I'm doing is a little Rails app with a Air desktop app written in Flex 3.  For the Rails portion I'm going with the standard REST actions with responses for html and xml.  The Air application then uses the REST api to communicate with the back end.  Everything is pretty straight forward, but getting flex to play nice was kind of frustrating.

The main problem was getting rails to accept the requests.  I started out with something like this:

  var service:HTTPService = new HTTPService();
  service.url = 'http://localhost:3000/sessions';
  service.addEventListener(ResultEvent.RESULT, complete);
  service.send({login:'user',password:'password'});

The first problem I ran into with this is that Rails was ignoring the requests and kept giving me a ActionController::InvalidAuthenticityToken error.  It took a little googling but I finally tracked it down to the CRSF protection in Rails 2; basically all forms submitted required a auth token to be sent with the data to validate  the form was generated by the server it is being submitted to.  This is only required for HTML forms being submitted, if the content-type is something else (like xml for my api services) the Authenticity Token is not required.

Once I got that figured out the requests were making it a little bit further but still getting hung up.  This time it was the xml parsing saying I was trying to add a second root node to the xml.  This was pretty obvious, I was passing login and password without being wrapped in anything, a couple little changes and this is where I'm at:

    var service:HTTPService = new HTTPService();
    service.method = 'POST';
    service.url = 'http://localhost:3000/sessions';
    service.contentType = HTTPService.CONTENT_TYPE_XML;
    service.addEventListener(ResultEvent.RESULT, complete);
    service.send({session:{login:'user',password:'password'}});

A little change on the server so it looks for the login and password within the session object and off to the races.  Well, sort of.  You might notice that I slipped in that service.method = "POST"; HTTPService supports POST, GET, PUT, DELETE etc for the method.  This was great so I banged out another method for logging out, basically the same as the previous one but with service.method = "DELETE".  This lead to a couple hours of debugging, googling and cURLing to try and figure out why logging out wasn't working.  Long story short, the only type of requests HTTPService actually does is POST and GET, no matter what you set the service method to.  So, reach back and pull out the hacks to come up with this for the logout action url:

    service.url = 'http://localhost:3000/sessions?_method=DELETE';

Now Rails can pick that out and knows that I'm trying to do a delete and routes the request correctly.  Now that I'm rolling it's easy to keep defining service objects and making calls to my Rails server but it's becoming clear that a lot of this can be abstracted away.  In my next post I'll talk about how I've started designing that abstraction and how it's going.