iOS Sort XML Data Coordinates (Example: SeismicXML)

[Darkroom]

what is the best course of action to sort XML data that has been parsed into strings, doubles, etc.?? particularly, listing the gps coordinates (doubles) from closest to furthest?

 

[drivefast]

i assume you parse your xml data such that you create several objects from the same class, and you store them in an array. i also assume you have a CLLocationCoordinate2D property that stores each object's latitude / longitude. instead of using @synthesize for setting this property, implement your own setter function, that would also create a "distance from here" member variable:

distanceFromHere = [crtLocation getDistanceFrom:[[CLLocation alloc] initWithLatitude:myObjectsCoordinate.latitude longitude:myObjectsCoordinate.longitude]];

so you reduced the problem to sorting the array of objects by the member called distanceFromHere. in your object's class create an ordering function that you can use for sorting:

- (NSComparisonResult)compareByDistanceFromHere:(MyClass *)objectICompareWith {
	return (distanceFromHere < objectICompareWith.distanceFromHere) ? NSOrderedAscending : NSOrderedDescending;
}

and finally, considering you added all your objects to a mutable array while parsing, you can use

[allMyObjects sortUsingSelector:@selector(compareByDistanceFromHere:)];

 

[Darkroom]

thanks for your help. a few minutes after i posted i actually found this little project where a developer is seasoning apple's SeismicXML example with distance sorting, with plans to include mapkit annotations. his work seems pretty involved for such a simplistic idea, but i guess that's development at its finest.

[EDIT] ouf! your solution seems much more streamlined. this project i am trying to study is a bit crazy and doesn't even seem to work.

 

[Darkroom]

Last edited by drivefast : Sep 28, 2009 at 11:00 PM. Reason: actually, distanceFromHere must be a property as well - making it a simple member variable is not going to cut it

yeah... in the end i simply created a @property float distanceFromUser; and assigned it the distance between the user's current location and another location with CLLocation's getDistanceFrom: method, and then sorted the array with an NSSortDescriptor before adding it to the tableview.

as usual, in hindsight the solution is quite simple.