Why does the property not get set in this method? - ios

Question

This is my method
- (void)populateLocationsToSort {
//1. Get UserLocation based on mapview
self.userLocation = [[CLLocation alloc] initWithLatitude:self._mapView.userLocation.coordinate.latitude longitude:self._mapView.userLocation.coordinate.longitude];
//Set self.annotationsToSort so any new values get written onto a clean array
self.myLocationsToSort = nil;
// Loop thru dictionary-->Create allocations --> But dont plot
for (Holiday * holidayObject in self.farSiman) {
// 3. Unload objects values into locals
NSString * latitude = holidayObject.latitude;
NSString * longitude = holidayObject.longitude;
NSString * storeDescription = holidayObject.name;
NSString * address = holidayObject.address;
// 4. Create MyLocation object based on locals gotten from Custom Object
CLLocationCoordinate2D coordinate;
coordinate.latitude = latitude.doubleValue;
coordinate.longitude = longitude.doubleValue;
MyLocation *annotation = [[MyLocation alloc] initWithName:storeDescription address:address coordinate:coordinate distance:0];
// 5. Calculate distance between locations & uL
CLLocation *pinLocation = [[CLLocation alloc] initWithLatitude:annotation.coordinate.latitude longitude:annotation.coordinate.longitude];
CLLocationDistance calculatedDistance = [pinLocation distanceFromLocation:self.userLocation];
annotation.distance = calculatedDistance/1000;
//Add annotation to local NSMArray
[self.myLocationsToSort addObject:annotation];
**NSLog(#"self.myLocationsToSort in someEarlyMethod is %#",self.myLocationsToSort);**
}
//2. Set appDelegate userLocation
AppDelegate *myDelegate = [[UIApplication sharedApplication] delegate];
myDelegate.userLocation = self.userLocation;
//3. Set appDelegate mylocations
myDelegate.annotationsToSort = self.myLocationsToSort;
}
In the bold line, self.myLocationsToSort is already null. I thought setting a value to nil was cleaning it out basically, ready to be re-used? I need to do so because this method is called once on launch and a second time after an NSNotification is received when data is gotten from the web. If I call this method again from the NSNotification selector, the new web data gets written on top of the old data and it spits out an inconsistent mess of values :)

Answer 1

Setting it to nil removes the reference to that object. If you are using ARC and it is the last strong reference to that object, the system autoreleases the object and frees its memory. In either case, it does not "clean it out and be ready for re-use", you need to re-allocate and initialize your object. If you would rather just remove all of the objects, and assuming myLocationsToSort is an NSMutableArray you can just call
[self.myLocationsToSort removeAllObjects];
Otherwise you need to do
self.myLocationsToSort = nil;
self.myLocationsToSort = [[NSMutableArray alloc] init];