Question

I am getting a warning from the Xcode 3.2.5 static analyser that I don’t quite understand, the warning is:

Warning: The receiver of message
‘horizontalAccuracy’ is nil and
returns a value of type
‘CLLocationAccuracy’ that will be
garbage
if([lastGoodLocation
horizontalAccuracy] <=
DESIREDACCURACY) {

The code compiles and runs fine, but I am just curious as to what is happening and how I might fix it.

@property (nonatomic, retain) CLLocation *lastGoodLocation;

@synthesize lastGoodLocation;

.

// CHECK FOR BEST LOCATION
if(lastGoodLocation == nil || [newLocation horizontalAccuracy] < [lastGoodLocation horizontalAccuracy]) {
    NSLog(@"NEWBEST: %0.0fm (%@)", [newLocation horizontalAccuracy], [newLocation timestamp]);
    [self setLastGoodLocation:newLocation];

    // DESIRED ACCURACY & GEOCODE
    if([lastGoodLocation horizontalAccuracy] <= DESIREDACCURACY) {

EDIT:

Can newLocation be returned as nil, this code is in:

locationManager:didUpdateToLocation:fromLocation:

Answer 1

You can get into the outer if when lastGoodLocation is nil (left-hand side of the || condition), and within that if block, you’re calling [lastGoodLocation horizontalAccuracy] on a possibly nil reference. Change the inner if to something like

// DESIRED ACCURACY & GEOCODE
if (lastGoodLocation != nil && ([lastGoodLocation horizontalAccuracy] <= DESIREDACCURACY))

It may be that #setLastGoodLocation actually sets lastGoodLocation, but the analyzer may not spot that.

EDIT:

The docs at developer.apple.com suggest that while oldLocation may be nil (on the first fix), newLocation probably shouldn’t be — if location isn’t working, I think you’d receive #locationManager:didFailWithError: instead.