potential leak issues - iphone

Question

Firstly Please tell me what is potential leak and why it comes.
Potential leak is coming...
Here is My code
-(NSArray*)calculateRoutesFrom:(CLLocationCoordinate2D) f to: (CLLocationCoordinate2D) t
{
//NSLog(#"maproute....5..");
NSString* saddr = [NSString stringWithFormat:#"%f,%f", f.latitude, f.longitude];
NSString* daddr = [NSString stringWithFormat:#"%f,%f", t.latitude, t.longitude];
NSError* error;
NSString* apiUrlStr = [NSString stringWithFormat:#"http://maps.google.com/maps?output=dragdir&saddr=%#&daddr=%#&dirflg=w", saddr, daddr];
NSURL* apiUrl = [NSURL URLWithString:apiUrlStr];
NSLog(#"api url: %#", apiUrl);
NSString *apiResponse = [NSString stringWithContentsOfURL:apiUrl encoding:NSUTF8StringEncoding error:&error];
NSLog(#"what is this");
NSString* encodedPoints = [apiResponse stringByMatching:#"points:\\\"([^\\\"]*)\\\"" capture:1L];
NSLog(#"maproute....4..");
return [self decodePolyLine:[encodedPoints mutableCopy]]; // Here is The potential leak
}
I tried doing this
return [self decodePolyLine:[encodedPoints mutableCopy]autorelease];
but it send to many time autorelease message.
What to do Please help.
-(NSMutableArray *)decodePolyLine: (NSMutableString *)encoded {
[encoded replaceOccurrencesOfString:#"\\\\" withString:#"\\"
options:NSLiteralSearch
range:NSMakeRange(0, [encoded length])];
NSInteger len = [encoded length];
NSInteger index = 0;
NSMutableArray *array = [[[NSMutableArray alloc] init] autorelease];
NSInteger lat=0;
NSInteger lng=0;
while (index < len) {
NSInteger b;
NSInteger shift = 0;
NSInteger result = 0;
do {
b = [encoded characterAtIndex:index++] - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
NSInteger dlat = ((result & 1) ? ~(result >> 1) : (result >> 1));
lat += dlat;
shift = 0;
result = 0;
do {
b = [encoded characterAtIndex:index++] - 63;
result |= (b & 0x1f) << shift;
shift += 5;
} while (b >= 0x20);
NSInteger dlng = ((result & 1) ? ~(result >> 1) : (result >> 1));
lng += dlng;
NSNumber *latitude = [[[NSNumber alloc] initWithFloat:lat * 1e-5] autorelease];
NSNumber *longitude = [[[NSNumber alloc] initWithFloat:lng * 1e-5] autorelease];
printf("[%f,", [latitude doubleValue]);
printf("%f]", [longitude doubleValue]);
CLLocation *loc = [[[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]] autorelease];
[array addObject:loc];
}
return array;
}

Answer 1

You correctly diagnosed the problem, that your mutableCopy is never getting released. But you said [self decodePolyLine:[encodedPoints mutableCopy] autorelease] didn't work. It can't, though, because you're missing a set of brackets in there. The correct solution, which does the autorelease on the string, is:
return [self decodePolyLine:[[encodedPoints mutableCopy] autorelease]];
You will get your too many releases if you did the autorelease on the resulting NSMutableArray, though, via something like this:
return [[self decodePolyLine:[encodedPoints mutableCopy]] autorelease];
This latter use of autorelease is problematic. But, the first proposed change should fix the problem.
Having said that, I'd suggest a further simplification of the code. I'd be wary about methods that change mutable parameters that I pass to them (unless that behavior is needed for some reason, which it doesn't appear to be the case here). I'd rather see:
-(NSMutableArray *)decodePolyLine:(NSString *)encodedInput {
{
NSString *encoded = [encodedInput stringByReplacingOccurrencesOfString:#"\\\\"
withString:#"\\"];
NSInteger len = [encoded length];
// the rest of your method here
}
Then you can invoke this simply as:
return [self decodePolyLine:encodedPoints];
This also has the coincidental virtue of completely eliminating the problematic statement.
Unrelated to your problem, you could simplify your lines that say:
NSNumber *latitude = [[[NSNumber alloc] initWithFloat:lat * 1e-5] autorelease];
NSNumber *longitude = [[[NSNumber alloc] initWithFloat:lng * 1e-5] autorelease];
to be:
NSNumber *latitude = [NSNumber numberWithFloat:lat * 1e-5];
NSNumber *longitude = [NSNumber numberWithFloat:lng * 1e-5];
Or even better, maybe retire NSNumber altogether with just
float latitude = lat * 1e-5;
float longitude = lng * 1e-5;
printf("[%f,", latitude);
printf("%f]", longitude);
CLLocation *loc = [[[CLLocation alloc] initWithLatitude:latitude
longitude:longitude] autorelease];