private void AddEarthquakesToList(List <Earthquake> earthquakes) { var entity = NSEntityDescription.EntityForName("Earthquake", managedObjectContext); var fetchRequest = new NSFetchRequest(); fetchRequest.Entity = entity; var date = (NSPropertyDescription)entity.PropertiesByName.ValueForKey(new NSString("date")); var location = (NSPropertyDescription)entity.PropertiesByName.ValueForKey(new NSString("location")); fetchRequest.PropertiesToFetch = new NSPropertyDescription[] { date, location }; fetchRequest.ResultType = NSFetchRequestResultType.DictionaryResultType; NSError error; foreach (var earthquake in earthquakes) { var arguments = new NSObject[] { earthquake.Location, earthquake.Date }; fetchRequest.Predicate = NSPredicate.FromFormat(@"location = %@ AND date = %@", arguments); var fetchedItems = NSArray.FromNSObjects(managedObjectContext.ExecuteFetchRequest(fetchRequest, out error)); if (fetchedItems.Count == 0) { if (string.IsNullOrEmpty(entity.Description)) { continue; } var managedEarthquake = new ManagedEarthquake(entity, managedObjectContext) { Magnitude = earthquake.Magnitude, Location = earthquake.Location, Date = earthquake.Date, USGSWebLink = earthquake.USGSWebLink, Latitude = earthquake.Latitude, Longitude = earthquake.Longitude }; managedObjectContext.InsertObject(managedEarthquake); } var gregorian = new NSCalendar(NSCalendarType.Gregorian); var offsetComponents = new NSDateComponents(); offsetComponents.Day = -14; // 14 days back from today NSDate twoWeeksAgo = gregorian.DateByAddingComponents(offsetComponents, NSDate.Now, NSCalendarOptions.None); // use the same fetchrequest instance but switch back to NSManagedObjectResultType fetchRequest.ResultType = NSFetchRequestResultType.ManagedObject; fetchRequest.Predicate = NSPredicate.FromFormat(@"date < %@", new NSObject[] { twoWeeksAgo }); var olderEarthquakes = NSArray.FromObjects(managedObjectContext.ExecuteFetchRequest(fetchRequest, out error)); for (int i = 0; i < olderEarthquakes.Count; i++) { managedObjectContext.DeleteObject(olderEarthquakes.GetItem <ManagedEarthquake> (i)); } if (managedObjectContext.HasChanges) { if (!managedObjectContext.Save(out error)) { Console.WriteLine(string.Format("Unresolved error {0}", error.LocalizedDescription)); } } } }
void FetchQuakes(object sender, EventArgs e) { fetchQuakesButton.Enabled = false; var jsonURL = new NSUrl("http://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_month.geojson"); var session = NSUrlSession.FromConfiguration(NSUrlSessionConfiguration.EphemeralSessionConfiguration); NSUrlSessionTask task = session.CreateDataTask(jsonURL, (data, response, error) => { if (data == null) { Console.WriteLine("Error connecting: {0}", error.LocalizedDescription); return; } NSError anyError; NSManagedObjectContext taskContext = CreatePrivateQueueContext(out anyError); var jsonDictionary = NSJsonSerialization.Deserialize(data, NSJsonReadingOptions.AllowFragments, out anyError); if (jsonDictionary == null) { Console.WriteLine("Error creating JSON dictionary: {0}", anyError.LocalizedDescription); return; } var featuresArray = (NSArray)jsonDictionary.ValueForKey((NSString)"features"); int totalFeatureCount = (int)featuresArray.Count; int numBatches = totalFeatureCount / BatchSize; numBatches += totalFeatureCount % BatchSize > 0 ? 1 : 0; for (int batchNumber = 0; batchNumber < numBatches; batchNumber++) { int rangeStart = batchNumber * BatchSize; int rangeLength = Math.Min(BatchSize, totalFeatureCount - batchNumber * BatchSize); NSArray featuresBatchArray = featuresArray.SubarrayWithRange(new NSRange(rangeStart, rangeLength)); // Create a request to fetch existing quakes with the same codes as those in the JSON data. // Existing quakes will be updated with new data; if there isn't a match, then create a new quake to represent the event. NSFetchRequest matchingQuakeRequest = NSFetchRequest.FromEntityName("Quake"); // Get the codes for each of the features and store them in an array. NSArray codesDump = (NSArray)featuresBatchArray.ValueForKeyPath((NSString)"properties.code"); matchingQuakeRequest.Predicate = NSPredicate.FromFormat("code in %@", codesDump); var rawFetch = taskContext.ExecuteFetchRequest(matchingQuakeRequest, out anyError); Quake[] allMatchingQuakes = Array.ConvertAll(rawFetch, item => (Quake)item); NSString[] codes = NSArray.FromArray <NSString> (codesDump); for (int k = 0; k < codes.Length; k++) { var code = codes [k]; var matchingQuakes = allMatchingQuakes.Where(q => q.Code == code).ToArray <Quake> (); Quake quake = null; int matchingLength = matchingQuakes.Length; switch (matchingLength) { case 0: //Insert new item quake = (Quake)NSEntityDescription.InsertNewObjectForEntityForName("Quake", taskContext); break; case 1: //Update existing item quake = matchingQuakes [0]; break; default: //Remove duplicates for (int i = 1; i < matchingQuakes.Length; i++) { taskContext.DeleteObject(matchingQuakes [i]); } quake = matchingQuakes [0]; break; } var result = featuresBatchArray.GetItem <NSDictionary> ((nuint)k); var quakeDictionary = (NSDictionary)result.ObjectForKey((NSString)"properties"); quake.UpdateFromDictionary(quakeDictionary); } if (!taskContext.Save(out anyError)) { Console.WriteLine("Error saving batch: {0}", anyError.LocalizedDescription); return; } taskContext.Reset(); } // Bounce back to the main queue to reload the table view and reenable the fetch button. NSOperationQueue.MainQueue.AddOperation(() => { ReloadTableView(); fetchQuakesButton.Enabled = true; }); }); task.Resume(); }