Memory Allocation increases in didSelectRowAtIndexPath

Question

Hello,

I'm testing my App and in a very simple view, each time a tap on a UITableView row, my allocation overall bytes get higher and higher and never go downs.

I don't have any special code there, so I created a new project from scratch with a very simple view, force one section and just three rows. In the didSelectRowAtIndexPath code do nothing, and fire it with instruments and memory allocation and, the memory goes up with every cell selection ...

Is this normal behaviour ?

thanks,

regards,

m.

EDIT

//
// RootViewController.m
// allocation
//
// Created by Raimon Fernandez Sirera on 31/5/10.
// Copyright Casa 2010. All rights reserved.
//

#import "RootViewController.h"


@interface RootViewController ()
- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath;
@end


@implementation RootViewController

@synthesize fetchedResultsController, managedObjectContext;


#pragma mark -
#pragma mark View lifecycle

- (void)viewDidLoad {
 [super viewDidLoad];

 // Set up the edit and add buttons.
 self.navigationItem.leftBarButtonItem = self.editButtonItem;

 UIBarButtonItem *addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(insertNewObject)];
 self.navigationItem.rightBarButtonItem = addButton;
 [addButton release];

 NSError *error = nil;
 if (![[self fetchedResultsController] performFetch:&error]) {
 /*
 Replace this implementation with code to handle the error appropriately.

 abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
 */
 NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
 abort();
 }
}

/*
- (void)viewWillAppear:(BOOL)animated {
 [super viewWillAppear:animated];
}
*/
/*
- (void)viewDidAppear:(BOOL)animated {
 [super viewDidAppear:animated];
}
*/
/*
- (void)viewWillDisappear:(BOOL)animated {
 [super viewWillDisappear:animated];
}
*/
/*
- (void)viewDidDisappear:(BOOL)animated {
 [super viewDidDisappear:animated];
}
*/

/*
 // Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
 // Return YES for supported orientations.
 return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
 */


- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath {

 cell.textLabel.text = [NSString stringWithFormat:@"my row %d",indexPath.row];
}


#pragma mark -
#pragma mark Add a new object

- (void)insertNewObject {

 // Create a new instance of the entity managed by the fetched results controller.
 NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
 NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity];
 NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

 // If appropriate, configure the new managed object.
 [newManagedObject setValue:[NSDate date] forKey:@"timeStamp"];

 // Save the context.
 NSError *error = nil;
 if (![context save:&error]) {
 /*
 Replace this implementation with code to handle the error appropriately.

 abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
 */
 NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
 abort();
 }
}


#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
 return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
 return 3;
}


// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

 static NSString *CellIdentifier = @"Cell";

 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
 if (cell == nil) {
 cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
 }

 // Configure the cell.
 [self configureCell:cell atIndexPath:indexPath];

 return cell;
}



/*
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
 // Return NO if you do not want the specified item to be editable.
 return YES;
}
*/


// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

 if (editingStyle == UITableViewCellEditingStyleDelete) {
 // Delete the managed object for the given index path
 NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];
 [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]];

 // Save the context.
 NSError *error = nil;
 if (![context save:&error]) {
 /*
 Replace this implementation with code to handle the error appropriately.

 abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
 */
 NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
 abort();
 }
 } 
}


- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
 // The table view should not be re-orderable.
 return NO;
}


#pragma mark -
#pragma mark Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
 // Navigation logic may go here -- for example, create and push another view controller.
 /*
 <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
 NSManagedObject *selectedObject = [[self fetchedResultsController] objectAtIndexPath:indexPath];
 // ...
 // Pass the selected object to the new view controller.
 [self.navigationController pushViewController:detailViewController animated:YES];
 [detailViewController release];
 */
}


#pragma mark -
#pragma mark Fetched results controller

- (NSFetchedResultsController *)fetchedResultsController {

 if (fetchedResultsController != nil) {
 return fetchedResultsController;
 }

 /*
 Set up the fetched results controller.
 */
 // Create the fetch request for the entity.
 NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
 // Edit the entity name as appropriate.
 NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];
 [fetchRequest setEntity:entity];

 // Set the batch size to a suitable number.
 [fetchRequest setFetchBatchSize:20];

 // Edit the sort key as appropriate.
 NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
 NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

 [fetchRequest setSortDescriptors:sortDescriptors];

 // Edit the section name key path and cache name if appropriate.
 // nil for section name key path means "no sections".
 NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
 aFetchedResultsController.delegate = self;
 self.fetchedResultsController = aFetchedResultsController;

 [aFetchedResultsController release];
 [fetchRequest release];
 [sortDescriptor release];
 [sortDescriptors release];

 return fetchedResultsController;
} 


#pragma mark -
#pragma mark Fetched results controller delegate


- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
 [self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
 atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

 switch(type) {
 case NSFetchedResultsChangeInsert:
 [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
 break;

 case NSFetchedResultsChangeDelete:
 [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
 break;
 }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
 atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
 newIndexPath:(NSIndexPath *)newIndexPath {

 UITableView *tableView = self.tableView;

 switch(type) {

 case NSFetchedResultsChangeInsert:
 [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
 break;

 case NSFetchedResultsChangeDelete:
 [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
 break;

 case NSFetchedResultsChangeUpdate:
 [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
 break;

 case NSFetchedResultsChangeMove:
 [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
 [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
 break;
 }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
 [self.tableView endUpdates];
}


/*
// Implementing the above methods to update the table view in response to individual changes may have performance implications if a large number of changes are made simultaneously. If this proves to be an issue, you can instead just implement controllerDidChangeContent: which notifies the delegate that all section and object changes have been processed. 

 - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
 // In the simplest, most efficient, case, reload the table view.
 [self.tableView reloadData];
}
 */


#pragma mark -
#pragma mark Memory management

- (void)didReceiveMemoryWarning {
 // Releases the view if it doesn't have a superview.
 [super didReceiveMemoryWarning];

 // Relinquish ownership any cached data, images, etc that aren't in use.
}


- (void)viewDidUnload {
 // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
 // For example: self.myOutlet = nil;
}


- (void)dealloc {
 [fetchedResultsController release];
 [managedObjectContext release];
 [super dealloc];
}


@end

Answer 1

If you are looking at the "All Allocations" field in the Allocations tool inside Instruments, this behaviour is totally normal. It is showing you the number of bytes ever allocated, and this number does not go down when any of that memory is deallocated.

You want to be looking at the "Live Bytes" field. You should also use the Leaks tool which will report actual memory leaks more reliably.