Need help to make iOS 14 Widget show content from from REST api

Question

The original question is at Apple forum but no one can help. https://developer.apple.com/forums/thread/654967?answerId=622833022#622833022

I decided to ask on SO.

Problem

I'm developing a widget extension that show content from REST api. It show the updated following stock info.

Widgets Code-along, part 3: Advancing timelines doesn't help me.

Investigation brings me a though "it is a bug of iOS beta":

public func timeline(
    for configuration: ConfigurationIntent,
    with context: Context,
    completion: @escaping (Timeline<Entry>) -> ()
  ) {
    print("Provider.timeline: ")

    var entries: [SimpleEntry] = []

    let currentDate = Date()
    entries.append(SimpleEntry(
      date: Calendar.current.date(byAdding: .second, value: 15, to: currentDate)!,
      configuration: configuration
    ))
    
    let timeline = Timeline(entries: entries, policy: reloadPolicy)

    completion(timeline)
  }

Above code print Provider.timeline: 14->19 times in just 1 second.

---

Here's my code to work with network request without success:

public func timeline(
    for configuration: ConfigurationIntent,
    with context: Context,
    completion: @escaping (Timeline<Entry>) -> ()
  ) {
    print("Provider.timeline: ")
    
    fetchStocks { (stocks: [Stock], error: Bool) in
      print("fetchStocks: stocks: ", stocks) 
      completion(getTimeLineFromStocks(stocks: stocks, for: configuration, with: context, reloadPolicy: .atEnd))
    }
}

func getTimeLineFromStocks(
    stocks: [Stock],
    for configuration: ConfigurationIntent,
    with context: Context,
    reloadPolicy: TimelineReloadPolicy
  ) -> Timeline<Entry> {
    var entries: [SimpleEntry] = []
    let currentDate = Date()
    entries.append(SimpleEntry(
      date: Calendar.current.date(byAdding: .second, value: 15, to: currentDate)!,
      configuration: configuration,
      stocks: stocks
    ))
    
    let timeline = Timeline(entries: entries, policy: reloadPolicy)
    
    return timeline
  }


  func fetchStocks(completion: @escaping ([Stock], Bool) -> Void) {
    // Fetch stocks info from API    
    myStockService.getSearchResults(searchTerm: "FIT", perPage: 5) { results, errorMessage in
      if !errorMessage.isEmpty {
        print("--> Search error: " + errorMessage)
        completion([], true)
      } else if results == nil {
        print("--> Search result with ERROR: nil results")
        completion([], true)
      } else {
        print("--> searchResults: ", results)
        completion(results!, false)
        // reloadTimeline()
      }
    }
  }



// ------- MyStockService.swift -------
// If I set breakpoint I can see the list of stocks
func getSearchResults(searchTerm: String,  perPage: Int, completion: @escaping QueryResult) {
    // 1
    dataTask?.cancel()
    
    // 2
    if var urlComponents = URLComponents(string: "https://****************/my-stocks") {
      urlComponents.query = "foo=bar"

      // 3
      guard let url = urlComponents.url else {
        return
      }
    
      // 4
      dataTask = defaultSession.dataTask(with: url) { [weak self] data, response, error in
        defer {
          self?.dataTask = nil
        }
        
        // 5
        if let error = error {
          self?.errorMessage += "DataTask error: " + error.localizedDescription + "\n"
        } else if
          let data = data,
          let response = response as? HTTPURLResponse,
          response.statusCode == 200 {
          
            // update the: self?.resultItems, self?.errorMessage
            self?.updateSearchResults(data, perPage: perPage)
          
          // 6
          DispatchQueue.main.async {
            completion(self?.resultItems, self?.errorMessage ?? "")
          }
        }
      }
      
      // 7
      dataTask?.resume()
    }
  }

  func updateSearchResults(....) {
     ... This fn convert data to [Stock] and assign it to resultItems 
  }

I got the log:

Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
--> Search error: DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled

fetchStocks: stocks:  []
--> Search error: DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled

fetchStocks: stocks:  []
2020-07-23 18:06:38.131476+0700 my-widgetExtension[5315:1272323] libMobileGestalt MobileGestaltCache.c:166: Cache loaded with 4563 pre-cached in CacheData and 53 items in CacheExtra.
--> Search error: DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled

fetchStocks: stocks:  []
Provider.timeline: 
Provider.timeline: 
Provider.timeline: 
--> Search error: DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled

fetchStocks: stocks:  []
--> Search error: DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled
DataTask error: cancelled

fetchStocks: stocks:  []
2020-07-23 18:06:39.751035+0700 my-widgetExtension[5315:1272388] [connection] nw_resolver_start_query_timer_block_invoke [C1] Query fired: did not receive all answers in time for api-t19.24hmoney.vn:443
2020-07-23 18:06:51.891582+0700 my-widgetExtension[5315:1272323] [widget] No intent in timeline(for:with:completion:)

Above code doesn't update or show Stock to the widget UI, it sometimes has some strange crashed.

Anyone can help me to make it work?

Answer 1

I return to widget development after ~3 months of waiting for it to be stable.

I can confirm that my above previous code basically works since I upgrade to Xcode Version 12.2 beta 2 (12B5025f) yesterday. But I need to delete the widget and create a new one to avoid outdated code.

--- Updated ---

iOS limit widget refreshment by some factor so content refreshing from API every 5 mins might not always work as I expected.

Please see the official docs about Refreshing Widgets Efficiently

As mentioned in the docs, use the following approaches to optimize your widget refreshes:

• Have the containing app prepare data for the widget in advance of when the widget needs it. Use a shared group container to store the data.
• Use background processing time in your app to keep shared data up to date. For more information, see Updating Your App with Background App Refresh.
• Choose the most appropriate refresh policy for the information being shown, as described in the preceding section.
• Call reloadTimelines(ofKind:) only when information the widget is currently displaying changes.
• When your app is in the foreground, has an active media session, or is using the standard location service, refreshes don’t count against the widget’s daily limit