public override NSView GetViewForItem(NSTableView tableView, NSTableColumn tableColumn, nint row)
{
string identifier = tableColumn.Identifier;
NSTableCellView cellView = (NSTableCellView)tableView.MakeView(identifier, this);
Quake quake = quakesSource [(int)row];
if (identifier == ColumnIdentifierPlace)
{
cellView.TextField.StringValue = quake.Location;
}
else if (identifier == ColumnIdentifierTime)
{
cellView.TextField.ObjectValue = quake.Date;
}
else if (identifier == ColumnIdentifierMagnitude)
{
cellView.TextField.ObjectValue = quake.Magnitude;
}
return(cellView);
}
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();
}