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();
}