Turns an NSURL's -query string into a dictionary. Sadly URL's allow keys to be declared multiple times, so it is a dictionary of String of the keys and arrays of Strings as the objects. [String: [String]]

NSURL+QueryDictionary.swift

extension NSURL
{
	@objc var queryDictionary:[String: [String]]? {
		get {
			if let query = self.query {
				var dictionary = [String: [String]]()
				
				for keyValueString in query.componentsSeparatedByString("&") {
					var parts = keyValueString.componentsSeparatedByString("=")
					if parts.count < 2 { continue; }
					
					var key = parts[0].stringByRemovingPercentEncoding!
					var value = parts[1].stringByRemovingPercentEncoding!
					
					var values = dictionary[key] ?? [String]()
					values.append(value)
					dictionary[key] = values
				}
				
				return dictionary
			}
			
			return nil
		}
	}
}

let query = url.queryDictionary
let code = query?["code"]

@romk1n As it returns an array of keys but there will likely only be one (didn't know there could be multiples before writing this) you'll likely want to use.

let query = url.queryDictionary
let code = query?["code"]?.first