Ufdjrw

I want to run 2 pieces of asynchronous code in one function and escape them. I want first to download the Reciter information and then download with these information the images that is associated with the Reciter. I'm using Firestore. I tried to work with DispatchQueue and DispatchGroup but I couldn't figure something out. I hope someone can help me :)

func getReciters(completion: @escaping (Bool) -> Void) 
 var reciters = [Reciter]()
 self.BASE_URL.collection(REF_RECITERS).getDocuments (snapchot, error) in
 if let error = error 
 debugPrint(error)
 completion(false)
 // TODO ADD UIALTERCONTROLLER MESSAGE
 return
 

 guard let snapchot = snapchot else debugPrint("NO SNAPSHOT"); completion(false); return 

 for reciter in snapchot.documents 
 let data = reciter.data()
 let reciterName = data[REF_RECITER_NAME] as? String ?? "ERROR"
 let numberOfSurahs = data[REF_NUMBER_OF_SURAHS] as? Int ?? 0

// **HERE I WANT TO DOWNLOAD THE IMAGES**
 self.downloadImage(forDocumentID: reciter.documentID, completion: (image) in
 let reciter = Reciter(name: reciterName, image: nil, surahCount: numberOfSurahs, documentID: reciter.documentID)
 reciters.append(reciter)
 )
 
 
 UserDefaults.standard.saveReciters(reciters)
 completion(true)
 

You need DispatchGroup.

• In the scope of the function declare an instance of DispatchGroup.


• In the loop before the asynchronous block call enter.


• In the loop inside the completion handler of the asynchronous block call leave.


• After the loop call notify, the closure will be executed after all asynchronous tasks have finished.

func getReciters(completion: @escaping (Bool) -> Void) 
 var reciters = [Reciter]()
 self.BASE_URL.collection(REF_RECITERS).getDocuments (snapchot, error) in
 if let error = error 
 debugPrint(error)
 completion(false)
 // TODO ADD UIALTERCONTROLLER MESSAGE
 return
 

 guard let snapchot = snapchot else debugPrint("NO SNAPSHOT"); completion(false); return 
 let group = DispatchGroup()

 for reciter in snapchot.documents 
 let data = reciter.data()
 let reciterName = data[REF_RECITER_NAME] as? String ?? "ERROR"
 let numberOfSurahs = data[REF_NUMBER_OF_SURAHS] as? Int ?? 0
 group.enter()

 self.downloadImage(forDocumentID: reciter.documentID, completion: (image) in
 let reciter = Reciter(name: reciterName, image: nil, surahCount: numberOfSurahs, documentID: reciter.documentID)
 reciters.append(reciter)
 group.leave()
 )
 
 group.notify(queue: .main) 
 UserDefaults.standard.saveReciters(reciters)
 completion(true)