Order UITableView cells by calculated distance (Parse) - objective-c

Question

I have a problem with the database created on parse. I have a table that shows me how many miles of the various local (once you download the list from DB) the problem is that I would order it for distance upward, but I do not know how to do. The code I used to calculate the distance is this:
- (id)initWithCoder:(NSCoder *)aCoder
{
self = [super initWithCoder:aCoder];
if (self) {
// Custom the table
// The className to query on
self.parseClassName = #"Ristoranti";
// The key of the PFObject to display in the label of the default cell style
self.textKey = #"NomeLocale";
// Whether the built-in pull-to-refresh is enabled
self.pullToRefreshEnabled = YES;
// Whether the built-in pagination is enabled
self.paginationEnabled = YES;
// The number of objects to show per page
self.objectsPerPage = 100;
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.distanceFilter = kCLDistanceFilterNone;
locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation;
if(IS_OS_8_OR_LATER) {
[locationManager requestWhenInUseAuthorization];
[locationManager requestAlwaysAuthorization];
}
[locationManager startUpdatingLocation];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(refreshTable:)
name:#"refreshTable"
object:nil];
}
- (void)refreshTable:(NSNotification *) notification
{
// Reload the recipes
[self loadObjects];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"refreshTable" object:nil];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
- (PFQuery *)queryForTable
{
PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
query.limit = 100;
[query orderByAscending:#"createdAt"];
return query;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath object:(PFObject *)object
{
static NSString *simpleTableIdentifier = #"RecipeCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:simpleTableIdentifier];
}
NSString *AntDef = [NSString stringWithFormat:#"%#", [object objectForKey:#"AnteprimaDefault"]];
if ([AntDef isEqualToString:#"Null"])
{
PFImageView *thumbnailImageView = (PFImageView*)[cell viewWithTag:100];
thumbnailImageView.image = [UIImage imageNamed:#"ImageDefault.png"];
thumbnailImageView.layer.cornerRadius = thumbnailImageView.frame.size.width / 2;
thumbnailImageView.clipsToBounds = YES;
thumbnailImageView.layer.borderWidth = 0.5;
thumbnailImageView.layer.borderColor = [UIColor lightGrayColor].CGColor;
}
else
{
PFFile *thumbnail = [object objectForKey:#"Anteprima1"];
PFImageView *thumbnailImageView = (PFImageView*)[cell viewWithTag:100];
thumbnailImageView.image = [UIImage imageNamed:#"placeholder.jpg"];
thumbnailImageView.file = thumbnail;
thumbnailImageView.layer.cornerRadius = thumbnailImageView.frame.size.width / 2;
thumbnailImageView.clipsToBounds = YES;
[thumbnailImageView loadInBackground];
}
Lat = [[object objectForKey:#"Latitudine"] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
Long = [[object objectForKey:#"Longitudine"] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
Latdouble = [Lat doubleValue];
Longdouble = [Long doubleValue];
NSArray *locations = [NSArray arrayWithObjects:[[CLLocation alloc] initWithLatitude:Latdouble longitude:Longdouble], nil];
//NSLog(#"LOCATIONS COORDINATE: %#", locations);
CLLocation *currentLocation = [[CLLocation alloc] initWithLatitude:locationManager.location.coordinate.latitude longitude:locationManager.location.coordinate.longitude];;
CLLocation *nearestLoc = nil;
CLLocationDistance nearestDis = FLT_MAX;
for (CLLocation *location in locations) {
CLLocationDistance distance = [currentLocation distanceFromLocation:location];
for (CLLocation *location in locations) {
distance = [currentLocation distanceFromLocation:location];
if (nearestDis > distance) {
nearestLoc = location;
nearestDis = distance;
}
}
text12 = [NSString stringWithFormat:#"%.1f Km", nearestDis/1000];
}
...
}
Thanks in advance :)

Answer 1

Assuming your response data from Parse.com is a NSArray.
I'd suggest:
Do the request.
Sort the NSArray
Reload Data.
Sorting the array could be done like this using the block: sortedArrayUsingComparator:^NSComparisonResult(id a, id b)
NSArray *sortedArray;
sortedArray = [initialDataArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
//Here do the method to compare if `a` is closer or `b` is closer
YourParseObject *aObject = (YourParseObject *)a;
YourParseObject *bObject = (YourParseObject *)b;
//Get Latitude & Longitude from a and b.
//return NSOrderedAscending or NSOrderedDescending according to which one of a or b is the closest, using your previous method I suppose to be working.
}];
So sortedArray will look like this:
{
YourParseObject the closest one
YourParseObject the second closest one
//...
YourParseObject the farthest one.
}
Once it's done:
[yourTableView reloadData]

Answer 2

I just encountered this issue today and found out that Parse.com has already implemented this solution:
If you're using Parse's PFQueryTableViewController.h, you'd want to add this into your queryForTable method:
(PFQuery *)queryForTable {
PFQuery *query = [PFQuery queryWithClassName:self.parseClassName];
[query whereKey:#"yourClassPFLocationField" nearGeoPoint:yourLocation];
return query;
}
The same applies if you're not using the PFQueryTable, just use that sorting method when loading the query.
Everything is on the PFQuery documentation :D