Rails: Pass Params Through Ajax - ruby-on-rails

Question

I need to pass params through javascript back to the server. At the moment, I pass them into javascript like so:
sendParams("<%= params[:q].to_json %>");
And then send them back like this:
function sendParams(q){
$.ajax({
url: '/mymodel/myaction',
type: 'post',
data: {'q':q},
contentType: 'json'
});
}
In my controller, I try to use them like I would any other params:
MyModel.where(params[:q])
But the params are coming back empty, even though firebug shows this in the POST tab:
q=%7B%26quot%3Bc%26quot%3B%3A%7B%26quot%3B0%26quot%3B%3A%7B%26quot%3Ba%26quot%3B%3A%7B%26quot%3B0%26quot%3B%3A%7B%26quot%3Bname%26quot%3B%3A%26quot%3Btitle%26quot%3B%7D%7D%2C%26quot%3Bp%26quot%3B%3A%26quot%3Bcont%26quot%3B%2C%26quot%3Bv%26quot%3B%3A%7B%26quot%3B0%26quot%3B%3A%7B%26quot%3Bvalue%26quot%3B%3A%26quot%3B2%26quot%3B%7D%7D%7D%7D%2C%26quot%3Bs%26quot%3B%3A%7B%26quot%3B0%26quot%3B%3A%7B%26quot%3Bname%26quot%3B%3A%26quot%3Bvotes_popularity%26quot%3B%2C%26quot%3Bdir%26quot%3B%3A%26quot%3Bdesc%26quot%3B%7D%7D%7D
Any idea why this information isn't getting processed by the where clause? What can I do to make the params Rails readable again?
UPDATE:
Started POST "/publications/search?scroll=active&page=6" for 127.0.0.1 at 2013-0
2-12 22:55:24 -0600
Processing by PublicationsController#index as */*
Parameters: {"scroll"=>"active", "page"=>"6"}
UPDATE 2:
The problem is apparently stemming from contentType. When I remove it, then q is sent as a Rails parameter. Unfortunately, q is still in JSON, resulting in the error:
undefined method `with_indifferent_access' for #<String:0x686d0a8>
How can I convert JSON to a params hash?

Answer 1

Your data parameter is wrong.
You have
data: {'q':q},
It should be
data: {q: 'q'},

Answer 2

There were a couple of issues that needed to be resolved for this to work. First, q wasn't being sent as a parameter to Rails, even though it was posting. The reason was because it was being treated as JSON data rather than as a parameter. I fixed this by removing the line:
contentType: 'json'
After that, the AJAX properly sent 'q', but Rails had trouble using it as it was in JSON. I had to parse it with ActiveSupport::JSON.decode, but this was throwing a 737: unexpected token error. I ran the code through (JSONlint)[http://jsonlint.com/], and it turns out that all the quotation marks had been escaped.
From there, there were two solutions. The obvious one was to use .html_safe like so:
sendParams("<%= params[:q].to_json.html_safe %>");
But this caused problems when the user inputed quotes. The safer alternative was to decode the escaped HTML entities after they were passed back to Rails like so:
ActiveSupport::JSON.decode(CGI.unescapeHTML(params[:q]))
And this did the trick.