Memory Allocation with ARC - No leaks but slowly heaping memory - ios

Question

I've started writing my first serious attempt at a hybrid, Cordova/Objective-C program for iOS, and I'm currently hitting some stumbling blocks regarding memory allocations. I need to get the user's Album art to display within the web view. I got the art to display successfully, but now there's a ton of memory being allocated.
Using the "Instruments" tool and comparing Generational Snapshots, I've narrowed my guilty culprits down to these methods - which I all wrote from scratch. But I'm confused - since I'm using automatic reference counting, and that I have everything in autorelease pools, that there shouldn't be any wasted memory. Funny thing is, I see no "leaks" being reported - just a heap that gets bigger, with more and more memory allocated.
I've attached some screenshots of the Instruments tool:
Here are direct links to the images since there is so much text:
http://i.imgur.com/rkc5dhA.png
http://i.imgur.com/U2esgBT.png
http://i.imgur.com/fmt3Mv4.png
Here's the contents of the "BukketHelper.M" class that I made (matches the header, no strong properties or any other definitions of any sort):
-(NSString *) convertULLToNSString:(NSNumber* )guid
{
return [NSString stringWithFormat:#"%llu", [guid unsignedLongLongValue]];
}
-(NSNumber *) convertStringToULL:(NSString *) guid
{
//get string to number
//this causes memory to not be released
unsigned long long ullvalue = strtoull([guid UTF8String], NULL, 10);
NSNumber *numberID = [[NSNumber alloc] initWithUnsignedLongLong:ullvalue];
return numberID;
}
Here's the contents of the "MediaQuery.M" class that I made (this matches the header exactly, no strong properties or other definitions):
-(MPMediaItem*) getMediaItemULL:(NSNumber*)guid
{
#autoreleasepool {
//run the query on
MPMediaQuery *query = [[MPMediaQuery alloc] init];
[query addFilterPredicate:[MPMediaPropertyPredicate predicateWithValue:guid forProperty:MPMediaItemPropertyPersistentID]];
//get and return the item
NSArray *mediaResults = [query items];
return [mediaResults firstObject];
}
}
-(MPMediaItem*) getMediaItem:(NSString*)guid
{
#autoreleasepool {
BukketHelper* bh = [[BukketHelper alloc] init];
return [self getMediaItemULL:[bh convertStringToULL:guid]];
}
}
-(UIImage*) getMediaAlbumArtAsUIImage:(NSString*)guid withQuality:(NSNumber*)quality withLength:(NSNumber*)length subsituteImageName:(NSString* )filename
{
return [self getMediaAlbumArtFromMediaItemAsUIImage:[self getMediaItem:guid] withQuality:quality withLength:length subsituteImageName:filename];
}
-(NSString*) getMediaAlbumArtAsBase64:(NSString*)guid withQuality:(NSNumber*)quality withLength:(NSNumber*)length subsituteImageName:(NSString* )filename
{
NSString *base64 = nil;
#autoreleasepool {
UIImage* rawImage = [self getMediaAlbumArtAsUIImage:guid withQuality:quality withLength:length subsituteImageName:filename];
NSData *imageData = nil;
if (rawImage != nil)
{
#autoreleasepool {
//this causes memory to not be released
imageData = UIImageJPEGRepresentation(rawImage, [quality floatValue]);
base64 = [imageData base64EncodedStringWithOptions:0];
}
}
}
return base64;
}
-(UIImage*) getMediaAlbumArtFromMediaItemAsUIImage:(MPMediaItem*)item withQuality:(NSNumber*)quality withLength:(NSNumber*)length subsituteImageName:(NSString* )filename
{
UIImage *rawImage = nil;
#autoreleasepool {
bool successfulArt = NO;
if (item != nil)
{
MPMediaItemArtwork *albumArt = [item valueForProperty:MPMediaItemPropertyArtwork];
if (albumArt != nil) {
#autoreleasepool {
//this causes memory to not be released
rawImage = [albumArt imageWithSize:CGSizeMake([length doubleValue], [length doubleValue])];
successfulArt = YES;
}
}
}
if (successfulArt == NO)
{
rawImage = [UIImage imageNamed:filename];
}
}
return rawImage;
}
So yeah - my question is: What am I doing wrong when it comes to memory allocation and leaks? My current tests are exclusively using album art - so "UIImage imageNamed" shouldn't be the issue (from it's caching). In addition, I've read that ARC cannot release CoreGraphics objects, which could also be the problem.
I really could use some help with this! Thank you!

Answer 1

I ran into the same problem. I think there's a bug in the framework which doesn't release the memory. Basically there's a huge spike in allocated memory each time func imageWithSize(size: CGSize) -> UIImage? is called.
If it helps you any, I noticed that if you call this function passing in the artwork.bounds.size (instead of creating a new image size each time) then the memory gets allocated only once and calling imageWithSize again (with the same dimensions) does not reallocate new memory. This appears to only be true if you pass in the size of the original artwork image and don't return a custom size. If you need a custom size, perhaps you can then resize the UIImage on your own and not rely on this buggy method.