Can someone help me with memory leak? - ios

Question

EDIT: I USE ARC IN PROJECT
I load annotations from plist like this:
[NSThread detachNewThreadSelector:#selector(loadPList) toTarget:self withObject:nil];
...
- (void) loadPList
{
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *path = [[documentPaths lastObject] stringByAppendingPathComponent:#"test.plist"];
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path]; // memory leak here
NSMutableArray *annotations = [[NSMutableArray alloc]init];
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray * annotationsToRemove = [ mapView.annotations mutableCopy ] ;
[ annotationsToRemove removeObject:mapView.userLocation ] ;
[ mapView removeAnnotations:annotationsToRemove ] ;
if ([[NSUserDefaults standardUserDefaults] boolForKey:#"blackKey"])
{
NSArray *ann = [dict objectForKey:#"Black"];
for(int i = 0; i < [ann count]; i++) {
NSString *coordinates = [[ann objectAtIndex:i] objectForKey:#"Coordinates"];
double realLatitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:1] doubleValue];
double realLongitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:0] doubleValue];
MyAnnotation *myAnnotation = [[MyAnnotation alloc] init];
CLLocationCoordinate2D theCoordinate;
theCoordinate.latitude = realLatitude;
theCoordinate.longitude = realLongitude;
myAnnotation.coordinate=CLLocationCoordinate2DMake(realLatitude,realLongitude);
myAnnotation.title = [[ann objectAtIndex:i] objectForKey:#"Name"];
myAnnotation.subtitle = [[ann objectAtIndex:i] objectForKey:#"Address"];
myAnnotation.icon = [[ann objectAtIndex:0] objectForKey:#"Icon"];
[mapView addAnnotation:myAnnotation];
[annotations addObject:myAnnotation];
}
}
});
}
All loads fine, but Memory leak tool shows me an leak.

Answer 1

You need to put the #autoreleasepool at the start of your method - with that dictionaryWithContentsOfFile: call outside of it, you're creating an autoreleased object without a pool, so it'll leak. Per the threading programming guide:
If your application uses the managed memory model, creating an
autorelease pool should be the first thing you do in your thread entry
routine. Similarly, destroying this autorelease pool should be the
last thing you do in your thread.
Also, can I ask why you to use NSThread for loading the plist rather than a dispatch_async()using a global queue? I don't often see dispatch_async() nested inside a thread detachment, so just curious.
EDIT:
To fix your memory leak, without disturbing your thread / GCD hybrid, call your method like this:
[NSThread detachNewThreadSelector:#selector(loadPList) toTarget:self withObject:nil];
And implement it like this:
- (void) loadPList
{
#autoreleasepool {
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *path = [[documentPaths lastObject] stringByAppendingPathComponent:#"test.plist"];
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path]; // memory leak here
NSMutableArray *annotations = [[NSMutableArray alloc]init];
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray * annotationsToRemove = [ mapView.annotations mutableCopy ] ;
[ annotationsToRemove removeObject:mapView.userLocation ] ;
[ mapView removeAnnotations:annotationsToRemove ] ;
if ([[NSUserDefaults standardUserDefaults] boolForKey:#"blackKey"])
{
NSArray *ann = [dict objectForKey:#"Black"];
for(int i = 0; i < [ann count]; i++)
{
NSString *coordinates = [[ann objectAtIndex:i] objectForKey:#"Coordinates"];
double realLatitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:1] doubleValue];
double realLongitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:0] doubleValue];
MyAnnotation *myAnnotation = [[MyAnnotation alloc] init];
CLLocationCoordinate2D theCoordinate;
theCoordinate.latitude = realLatitude;
theCoordinate.longitude = realLongitude;
myAnnotation.coordinate=CLLocationCoordinate2DMake(realLatitude,realLongitude);
myAnnotation.title = [[ann objectAtIndex:i] objectForKey:#"Name"];
myAnnotation.subtitle = [[ann objectAtIndex:i] objectForKey:#"Address"];
myAnnotation.icon = [[ann objectAtIndex:0] objectForKey:#"Icon"];
[mapView addAnnotation:myAnnotation];
[annotations addObject:myAnnotation];
}
}
}
);
}
}

Answer 2

If nothing else, you need an autorelease pool. To quote from the documentation for detachNewThreadSelector, "the method aSelector is responsible for setting up an autorelease pool for the newly detached thread and freeing that pool before it exits."
Personally, I'd probably just invoke loadPlist via GCD rather than detachNewThreadSelector, and then you don't need to worry about an autorelease pool:
dispatch_async(get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self loadPlist];
});

Answer 3

NSMutableArray *annotations = [[NSMutableArray alloc]init]; // Never released
NSMutableArray * annotationsToRemove = [ mapView.annotations mutableCopy ] ; // Never released
MyAnnotation *myAnnotation = [[MyAnnotation alloc] init]; // Never released
Your method should look like this:
- (void) loadPList {
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *path = [[documentPaths lastObject] stringByAppendingPathComponent:#"test.plist"];
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile:path]; // memory leak here
NSMutableArray *annotations = [[[NSMutableArray alloc] init] autorelease];
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray * annotationsToRemove = [[mapView.annotations mutableCopy] autorelease];
[annotationsToRemove removeObject:mapView.userLocation] ;
[mapView removeAnnotations:annotationsToRemove] ;
if ([[NSUserDefaults standardUserDefaults] boolForKey:#"blackKey"])
{
NSArray *ann = [dict objectForKey:#"Black"];
for(int i = 0; i < [ann count]; i++) {
NSString *coordinates = [[ann objectAtIndex:i] objectForKey:#"Coordinates"];
double realLatitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:1] doubleValue];
double realLongitude = [[[coordinates componentsSeparatedByString:#","] objectAtIndex:0] doubleValue];
MyAnnotation *myAnnotation = [[[MyAnnotation alloc] init] autorelease];
CLLocationCoordinate2D theCoordinate;
theCoordinate.latitude = realLatitude;
theCoordinate.longitude = realLongitude;
myAnnotation.coordinate=CLLocationCoordinate2DMake(realLatitude,realLongitude);
myAnnotation.title = [[ann objectAtIndex:i] objectForKey:#"Name"];
myAnnotation.subtitle = [[ann objectAtIndex:i] objectForKey:#"Address"];
myAnnotation.icon = [[ann objectAtIndex:0] objectForKey:#"Icon"];
[mapView addAnnotation:myAnnotation];
[annotations addObject:myAnnotation];
}
}
});
}