ARC 内存泄露的可能性

``

CGContextRef context = CGBitmapContextCreate(NULL, target_w, target_h, 8, 0, rgb, bmi);

CGColorSpaceRelease(rgb);

UIImage *pdfImage = nil;

if (context != NULL) {
    CGContextDrawPDFPage(context, page);
    
    CGImageRef imageRef = CGBitmapContextCreateImage(context);
    CGContextRelease(context);

    pdfImage = [UIImage imageWithCGImage:imageRef scale:screenScale orientation:UIImageOrientationUp];
    CGImageRelease(imageRef);
} else {
   CGContextRelease(context);
}

``

``
__weak typeof(self) weakSelf = self;

void (^ loadThumbnailBlock)(NSIndexPath *indexPath) = ^ (NSIndexPath *indexPath) {
    Page *page = [weakSelf.fetchedResultsController objectAtIndexPath:indexPath];
    [weakSelf loadThumbnailForPage:page forIndexPath:indexPath];
};

``

``
__block NSBlockOperation *operation = [[NSBlockOperation alloc] init];
__weak typeof(self)weakSelf = self;
__weak typeof(operation)weakOp = operation;

MMVoidBlock thumbnailOperationBlock = ^ {
    if (!weakOp.isCancelled) {
        workerBlock();
    }
    
    [weakSelf.thumbnailOperationList removeObjectForKey:key];
};

[operation addExecutionBlock:thumbnailOperationBlock];

``