ios swift check version

CheckVersion.swift

func checkVersion(appID: String, complete: (hasNewVersion: Bool, downloadAddr: String?) -> Void) {        
        NSURLSession.sharedSession().dataTaskWithURL(NSURL(string: "https://itunes.apple.com/lookup?id=\(appID)")!) { (data, response, error) -> Void in
            dispatch_async(dispatch_get_main_queue()) { () -> Void in
                if error != nil || data == nil {
                    complete(hasNewVersion: false, downloadAddr: nil)
                    return
                }
                do {
                    let json = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.MutableContainers)
                    if let all = json as? NSDictionary {
                        if let results = all["results"] as? NSArray {
                            if results.count == 0 {
                                complete(hasNewVersion: false, downloadAddr: nil)
                                return
                            }
                            if let result = results.objectAtIndex(0) as? NSDictionary {
                                if let version = result["version"] as? String {
                                    if let downUrl = result["trackViewUrl"] as? String {
                                        if version != Util.curVersion {
                                            complete(hasNewVersion: true, downloadAddr: downUrl)
                                            return
                                        }
                                    }
                                }
                                
                            }
                        }
                    }
                    complete(hasNewVersion: false, downloadAddr: nil)
                } catch {
                    complete(hasNewVersion: false, downloadAddr: nil)
                }
            }
        }.resume()
    }
    
  var curVersion: String {
        
        if let info = NSBundle.mainBundle().infoDictionary as NSDictionary? {
            let shortVersion: AnyObject? = info["CFBundleShortVersionString"]
            let buildVersion: AnyObject? = info["CFBundleVersion"]
            return "\(shortVersion!).\(buildVersion!)"
        }
        return "unknown"
    }