Convert a JS function to Objective C - repost

I have a JavaScript function with 210 LOC which makes a POST request to an URL. I get the result, parse the html and I convert the informations to a JSON with some properties. I need someone to convert this JS function to Objective C class. The request to the URL needs to be done in the background thread and return the result by calling a callback block in the UI main thread with and NSError if something went wrong with the request. The callback must also include the request result in case of success containing a NSDictionary with the same properties I use in my JS function.