Objective-c for the iphone: Mystery memory leak - iphone

Question

My application seems to have 4 memory leaks (on the device, running instruments).
The memory leaks seems to come from this code:
NSURL *url = [self getUrl:destination];
[destination release];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:#"GET"];
[request addValue:#"application/json" forHTTPHeaderField:#"content-type"];
NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
[request release];
[connection release];
EDIT: added code for getUrl
- (NSURL *)getUrl:(NSString *)actionUrl
{
NSString *rawUri = [[NSString alloc]initWithFormat:#"%#/%#", kBaseUrl, actionUrl];
NSURL *url = [[[NSURL alloc] initWithString:rawUri] autorelease];
[rawUri release];
return url;
}
I am releasing all my objects as far as I can see but it's still showing this as the source of the 4 memory leaks.
This is on the Device running 3.1.3
Is it acceptable to have a few memory leaks in your app or do they all have to go?
EDIT: I've added autorelease to getUrl. However it still shows up with memory leaks
EDIT2: The behaviour is rather strange. I launch the app and hit the button that makes this call once. 4 leaks are discovered. I press back and hit the button again, and keep doing this a few times, and still only 4 leaks. However, if I wait a few seconds and then press the button a gain a few more times, 9 leaks are discovered. It's not a small 128 byte leak, but it's 1.61KB at this point.
EDIT3: Here is the connectionDidFinishLoading
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
SBJSON *jsonParser = [[SBJSON alloc] init];
NSString *jsonString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
[receivedData setLength:0];
[receivedData release];
[self.delegate dataReceived:[jsonParser objectWithString:jsonString]]; // See method below
[jsonParser release];
[jsonString release];
}
The delegate gets the data, then transforms it (and in return passes it on to another delegate once the product is constructed)
- (void)dataReceived:(id)data
{
NSMutableArray *myObjects = [[NSMutableArray alloc]init];
ObjectFactory *objectFactory = [[ObjectFactory alloc]init];
// Only one object
if ([data isKindOfClass:[NSDictionary class]])
{
Object *object = [objectFactory buildObject:data];
[myObjects addObject:object];
[object release];
}
// Multiple objects
if ([data isKindOfClass:[NSArray class]])
{
for (NSDictionary *objectSrc in data)
{
Object *object = [objectFactory buildObject:post];
[myObjects addObject:object];
[object release];
}
}
[objectFactory release];
[self.delegate objectsReceived:myObjects];
}
EDIT4:
Something I did notice is that the object "ConnectionObject" that contains the NSUrlConnection, never seem to be deallocated.
I put a breakpoint on dealloc which calls [connection release]
This dealloc is never called. All the deallocs are called down the chain except for this one.
I tried [connection cancel] in the "connectionDidFinishLoading" call to see if that helped but not at all.
This sure is a mystery to me...

Answer 1

You are releasing something you shouldn't:
NSURL *url = [self getUrl:destination];
// the returned url should have been autoreleased by the getUrl: method
// so you shouldn't release it again
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[url release]; // don't do this!
Remember that you should only release objects that were created using alloc, new or retain . Objects returned from other methods are always in an auoreleased state (by convention).