Advice on MKAnnotation and NSString memory leak issues - ios

Question

I'm making an app that displays the user on the map along with multiple restaurant listings. When the user taps a pin, it stores the coordinates from the annotation and compares them against the users to ensure they are different. Once it is determined that they are different, it sends the coordinates of the business along with the coordinates of the user to Google to request directions. The code is working fine, but in order for it to do so I had to declare a few variables in ways that cause memory leaks. I'm hoping to clean the code up and learn where I erred and the proper way this should be handled.
So below is my code for getting the coordinates from the annotation that was tapped. If I attempt to initialize selectedAnnotation and allocate it's memory in say viewDidLoad by putting selectedAnnotation = [[MapLocation alloc] init]; Then it still shows up as a memory leak. And for reference, selectedAnnotation is a MapLocation(that conforms to MKAnnotation) variable, and as a property I have it (nonatomic, retain) and #synthesize(d).
I thought as long as I allocated it in memory, so long as I set its value to nil in viewDidUnload and released it in dealloc, that there should be no memory issues. What am I missing? Below is a screen shot of my memory leaks when I allocate the memory for selectedAnnotation in viewDidLoad along with the code provided below. If I have already allocated the memory, and check that the variable exists, why would it allocate the memory for the variable again? This happens for any restaurant pin I click on, but obviously not on the user's pin, because I have the code to release it in that case.
-(void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view
{
//NSLog(#"Selected annotation view");
// if we don't have the place holder already allocated
// lazy load the MapLocation placeholder variable
if(!selectedAnnotation)
{
selectedAnnotation = [[MapLocation alloc] init];
}
// save the annotation clicked
selectedAnnotation = view.annotation;
// if the annotation selected was is the same as the user's location
if((selectedAnnotation.coordinate.latitude == savedUserLocation.coordinate.latitude) && (selectedAnnotation.coordinate.longitude == savedUserLocation.coordinate.longitude))
{
// set it to nil and release it
selectedAnnotation = nil;
[selectedAnnotation release];
}
}
I'm having similar trouble with memory issues with the method below. I'm bringing in the JSON data from Google, to extract the address and coordinates of the user's location to display in the AnnotationView. I created all the necessary Arrays and Dictionaries to access the information, but once I allocate the memory for them and assign their values to savedUserLocation, if I try releasing say the NSDictionary variable userLocation, even as the last line of code in this method, the app crashes due to "[CFDictionary release]: message sent to deallocated instance 0x83ccb60". I'm pretty sure it's because I'm setting the values in savedUserLocation via pointer, and once the memory is released that information no longer exists, so what would be the proper way to allocate/release the memory to where I can access the information, without causing memory leaks? I've also tried using autorelease, but the same issues persist.
Here is the code that places the user pin.
- (void)fetchedData:(NSData *)responseData
{
//parse out the json data
NSError *error;
NSDictionary *json = [NSJSONSerialization
JSONObjectWithData:responseData //1
options:kNilOptions
error:&error];
NSArray *results = [json objectForKey:#"results"]; //2
NSUInteger counter = [results count];
NSDictionary *userLocation = [[NSDictionary alloc] init];
//NSString *address = [[NSString alloc] init];
for(NSUInteger i=0; i < counter; i++)
{
userLocation = [results objectAtIndex:i];
// 2) Get the funded amount and loan amount
NSString *address = [[NSString alloc] initWithString:[userLocation objectForKey:#"formatted_address"]];
NSArray *types = [userLocation objectForKey:#"types"];
NSDictionary *geometry = [userLocation objectForKey:#"geometry"];
NSDictionary *location = [geometry objectForKey:#"location"];
float lat = [[location objectForKey:#"lat"] floatValue];
float lon = [[location objectForKey:#"lng"] floatValue];
CLLocationCoordinate2D newCoordinates;
newCoordinates.latitude = lat;
newCoordinates.longitude = lon;
// count how many types there are
NSUInteger numberOfTypes = [types count];
NSString *type = [[NSString alloc] init];
for(NSUInteger j=0; j < numberOfTypes; j++)
{
type = [types objectAtIndex:j];
if([type rangeOfString:#"street_address" options:NSCaseInsensitiveSearch].location != NSNotFound)
{
NSLog(#"%#", address);
if(!savedUserLocation)
{
savedUserLocation = [[MapLocation alloc] init];
}
[savedUserLocation setTitle:#"You are here!"];
[savedUserLocation setSubtitle:address];
[savedUserLocation setCoordinate:newCoordinates];
}
}
}
// determine which location is closest to the user by calling this function
MapLocation *closestLocation = [self determineClosestLocationToUser:allLocations locationOfUser:savedUserLocation];
// send in the user location and the closest store to them to determine appropriate zoom level and
// to center the map between the two
[self determineMapCenterAndZoomLevelFromUser:savedUserLocation andClosestLocation:closestLocation];
if(!pinDropped)
{
// add the annotation to the map and then release it
[mapView addAnnotation:savedUserLocation];
pinDropped = true;
}
}
Thanks for any and all help/suggestions/advice. I'd really like to understand the nuts and bolts of what I'm doing wrong, as I thought I had a pretty decent grasp on it.

Answer 1

In didSelectAnnotationView, you have this code:
selectedAnnotation = nil;
[selectedAnnotation release];
This causes a memory leak because you are setting selectedAnnotation to nil and then calling release on it.
The call to release does nothing because selectedAnnotation is nil at that point and a call to nil does nothing. This means the memory that had been allocated is never released but since the pointer variable has been set to nil, when didSelectAnnotationView is called again, your code allocates a new object.
You should switch the order of the two statements (call release first and then set to nil).
However, you don't need to alloc a new object just to keep a reference to the "selected annotation".
Declaring a regular ivar (not a retain property) and just setting it equal to the selected annotation should work.
In addition, the map view already has a property called selectedAnnotations which you should be able to use (so you don't need to maintain your own ivar or property). The map view's property is an NSArray but will always contain either 0 or 1 object(s). Be sure to check its count before accessing the object at index 0.
In fetchedData, you have several memory leaks caused by unnecessary alloc calls.
They are not needed because after calling alloc, you are then directly assigning a new reference to the pointer you just allocated memory for.
For example, userLocation is alloc'd before the for-loop but then inside the loop you directly point that variable to an object in the results array.
This means the memory that had originally been allocated for userLocation becomes abandoned with no reference to it. When you try to call release on userLocation, it is trying to release an object that was not allocated by code in fetchedData.
To fix at least userLocation, just declare the variable and don't alloc/init/release it.
The variables address and type (the NSString) have a similar issue.