Nested dataTaskWithRequest in Swift tvOS -

i'm c# developer convert swift tvos , starting learn. i've made progress, not sure how handle nested calls json. sources different providers can't combine query.

how wait inner request complete tvseries has poster_path? there better way add show collection , process poster path loading in thread doesn't delay ui experience?

    func downloadtvdata() {     let url_btv = nsurl(string: btv_url_base)!     let request_btv = nsurlrequest(url: url_btv)     let session_btv = nsurlsession.sharedsession()      //get series data     let task_btr = session_btv.datataskwithrequest(request_btv) { (data_btv, response_btv, error_btv) -> void in         if error_btv != nil {             print (error_btv?.description)         } else {             {                 let dict_btv = try nsjsonserialization.jsonobjectwithdata(data_btv!, options: .allowfragments) as? dictionary<string, anyobject>                 if let results_btv = dict_btv!["results"] as? [dictionary<string, anyobject>]{                     obj_btv in results_btv {                         let tvshow = tvseries(tvdict: obj_btv)                         //for each tv series try load poster_path secondary provider                         if let str = obj_btv["title"] as? string!{                             let escapedstring = str?.stringbyaddingpercentencodingwithallowedcharacters(.urlqueryallowedcharacterset())!                              if let url = nsurl(string: self.search_url_base + escapedstring!) {                                 let request = nsurlrequest(url: url)                                 let session = nsurlsession.sharedsession()                                 let task = session.datataskwithrequest(request) { (data, response, error) -> void in                                     if error != nil {                                         print (error?.description)                                     } else {                                         {                                             let dict = try nsjsonserialization.jsonobjectwithdata(data!, options: .allowfragments) as? dictionary<string, anyobject>                                              if let results = dict!["results"] as? [dictionary<string, anyobject>] {                                                  //iterate through poster array                                                 obj in results {                                                     if let path = obj["poster_path"] as? string {                                                         tvshow.posterpath = path                                                         break                                                     }                                                 }                                             }                                         } catch let error nserror {                                             print(error.description)                                         }                                     }                                 }                                 task.resume()                             }                         }                         self.tvseries.append(tvshow)                     }                     dispatch_async(dispatch_get_main_queue()){                         self.collectionview.reloaddata()                     }                 }             }  catch let error nserror {                 print(error.description)             }         }     }     task_btr.resume() } 

thanks help!

i recommend breaking things apart multiple methods, callbacks sequence operations, , utilizing swift's built-in throws error handling mechanism. here's example, not perfect, might starting point:

class tvseries {     let title: string     var posterpath: string?      enum error: errortype {         case malformedjson     }      init(tvdict: [string: anyobject]) throws     {         guard let title = tvdict["title"] as? string else {             throw error.malformedjson         }          self.title = title     }      static func loadallseries(completionhandler: [tvseries]? -> void)     {         nsurlsession.sharedsession().datataskwithurl(nsurl(string: btv_url_base)!) { data, response, error in             guard let data = data else {                 print(error)                 completionhandler(nil)                 return             }              {                 completionhandler(try fromjsondata(data))             }             catch let error {                 print(error)             }         }.resume()     }      static func fromjsondata(jsondata: nsdata) throws -> [tvseries]     {         guard let dict = try nsjsonserialization.jsonobjectwithdata(jsondata, options: .allowfragments) as? [string: anyobject] else {             throw error.malformedjson         }          guard let results = dict["results"] as? [[string: anyobject]] else {             throw error.malformedjson         }          return try results.map {             return try tvseries(tvdict: $0)         }     }      func loadposterpath(completionhandler: () -> void)     {         guard let searchpath = title.stringbyaddingpercentencodingwithallowedcharacters(.urlqueryallowedcharacterset()) else {             completionhandler()             return         }          let url = nsurl(string: search_url_base)!.urlbyappendingpathcomponent(searchpath)         nsurlsession.sharedsession().datataskwithurl(url) { [weak self] data, response, error in             defer { completionhandler() }              guard let strongself = self else { return }              guard let data = data else {                 print(error)                 return             }              {                 strongself.posterpath = try tvseries.posterpathfromjsondata(data)             }             catch let error {                 print(error)             }         }.resume()     }      static func posterpathfromjsondata(jsondata: nsdata) throws -> string?     {         guard let dict = try nsjsonserialization.jsonobjectwithdata(jsondata, options: .allowfragments) as? [string: anyobject] else {             throw error.malformedjson         }          guard let results = dict["results"] as? [[string: anyobject]] else {             throw error.malformedjson         }          result in results {             if let path = result["poster_path"] as? string {                 return path             }         }          return nil     } } 

it might worth time rxswift or alamofire, these kinds of data-conversion / sequencing operations.