This is my first post so I hope the formatting is ok.
I'm getting this leak "Potential leak of an object on line" and I can't figure it out. Perhaps I'm looking at it too hard and therefore I can't see the problem. Could someone help me out?
The line is question is: appDelegate.imageText
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
PListFirstAppDelegate *appDelegate = (PListFirstAppDelegate *)[[UIApplication sharedApplication]delegate];
appDelegate.imageText= [[NSString alloc]initWithFormat:#"%#",[[array objectAtIndex:indexPath.row]objectForKey:#"image"]];
//NSLog(#"%#", appDelegate.imageText);
NavigationalDescription *detailViewController = [[NavigationalDescription alloc] initWithNibName:#"NavigationalDescription" bundle:nil];
// Pass the selected object to the new view controller.
[self.navigationController pushViewController:detailViewController animated:YES];
[detailViewController release];
}
Every time you use any init method to instantiate an object, you must release it somewhere, or call autorelease.
Class methods that return something should always be autoreleased.
So instead of using [[NSString alloc] initWithFormat...]
do [NSString stringWithFormat:#"%#", myString] instead.
Replace code at
appDelegate.imageText= [[NSString alloc]initWithFormat:#"%#",[[array objectAtIndex:indexPath.row]objectForKey:#"image"]];
with
appDelegate.imageText= [NSString stringWithFormat:#"%#",[[array objectAtIndex:indexPath.row] objectForKey:#"image"]];
You should add an autorelease call at the end of that line.
iPad won't let me copy paste code :( so no example right now.
appDelegate.imageText= [[[NSString alloc]initWithFormat:#"%#",[[array objectAtIndex:indexPath.row]objectForKey:#"image"] ] autorelease];
You are saying delegating control over the memory management to the imagetext instance. They should retain the string as they need it.
appDelegate.imageText= [[NSString alloc]initWithFormat:#"%#",[[array objectAtIndex:indexPath.row]objectForKey:#"image"]];
you are assigning an allocated string to image text property. the property assignment should be to an autoreleased string. imageText should be a retain property, therefore retaining the falue of the string being assigned to it. If it's retain, you are double retaining, therefore leaking the object.
Related
I get leaks if I dont put it in dealloc. I get a crash EXC_BAD_ACCESS If I do. I cannot see anything wrong with this code. The bad access is pointed at [events release]. Have I made a mistake in the code below or is Instruments just having a laugh at my expense?
events is an NSArray
#interface EventsViewController : UITableViewController
{
#private
NSArray *events;
}
- (void)viewDidLoad
{
events = [[self getEvents] retain];
}
- (void)dealloc
{
[events release];
[super dealloc];
}
- (NSArray*)getEvents
{
NSMutableArray *response = [[[NSMutableArray alloc] init] autorelease];
//Some sql
while(sqlite3_step(statement) == SQLITE_ROW)
{
Event *event = [[[Event alloc] init] autorelease];
event.subject = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 0)];
[response addObject:event];
}
return response;
}
Update
A lot of you are saying the code is fine which is a plus. I dont manipulate events elsewhere - I have removed any code that does to try and single out the crash. Perhaps its in the parent view?
This is the click event that pushes the EventsViewController:
- (void)eventsClick:(id)sender
{
EventsViewController *eventsViewController = [[EventsViewController alloc] initWithNibName:#"EventsViewController" bundle:nil];
eventsViewController.anywhereConnection = anywhereConnection;
eventsViewController.contact = contact;
[[self navigationController] pushViewController:eventsViewController animated:YES];
[eventsViewController release];
}
The crash is actually happening when I return to the parent view. (I think it is considered a parent in this scenario). But perhaps the [eventsViewController release] just triggers dealloc in the EventViewController.
Have you considered just refactoring your code to use ARC? It works with iOS 4 and up and will make your life a lot easier. There are plenty of tutorials out there that will guide you how to do it, and will remove the need to manually figure out the nuances of memory management.
If your Events object has property 'subject' set as assign, then the results of stringWithUTF8String: will not be retained. (Same thing if Events is a C++ object.)
The stringWithUTF8String: method returns an auto-released object that will be released at the next turn of the event loop.
There is a huge difference when you reference a variable via "self", and when you don't.
When you use
events = [[self getEvents] retain];
the memory allocated in getEvents never gets stored in the class property and is basically a leak.
You need to use
self.events = [self getEvents]; // no need to use retain if property is correctly defined.
Then
[events release];
should work fine.
try putting
events = nil;
in dealloc.
I have these two buttons hooked up to these two methods (they're nearly identical)
-(void)moveOneImageNewer{
int num = [numberOfImage intValue];
num--;
numberOfImage = [[NSString stringWithFormat:#"%i",num] retain];
//Load the image
[self loadImage];
}
-(void)moveOneImageOlder{
int num = [numberOfImage intValue];
num++;
numberOfImage = [NSString stringWithFormat:#"%i",num];
//Load the image
[self loadImage];
}
If I hit either of them twice (or once each, basically if they get called a total of two times) I get an EXC_BAD_ACCESS. If I throw a retain on: numberOfImage = [[NSString stringWithFormat:#"%i",num]retain] it's fine though. Can someone explain why this is? I did an NSZombie on the instruments and traced it back to this stringWithFormat call. Thanks in advance!
+stringWithFormat: doesn't contain 'new', 'alloc', 'copy', or 'retain', so it should be expected that you have to retain the return value of it if you want the new NSString it creates to stick around.
Edited to include this handy link duskwuff kindly dug up: http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html#//apple_ref/doc/uid/20000994-BAJHFBGH
If numberOfImage is a properly declared property, e.g.
#property (copy) NSString *numberOfImage;
and it was properly synthesized (in the #implementation section for the class):
#synthesize numberOfImage;
then you can do:
- (void) moveOneImageNewer
{
self.numberOfImage = [NSString stringWithFormat: #"%i", [self.numberOfImage intValue] - 1];
// Load the image
[self loadImage];
}
The property setter will take care of retaining the string and, if necessary, releasing the previous string.
FWIW, why on earth is numberOfImage a string? Why not a simple int?
numberOfImage is an instance variable or property of your class, right?
You are setting it to a stringWithFormat (which returns an auto-released NSString) without claiming ownership of that object (by calling retain).
If you do not retain it, it will get auto-released before the method is called again (and then the first line will fail, as it tries to access the previously set, now auto-released value).
Consider using properties, they have auto-generated memory management code (including releasing the old NSString when you set the new one).
You haven't retained the string object in "moveOneImageOlder", so that object gets autoreleased at the end of the event cycle and points to nothing. That's why you get the EXC_BAD_ACCESS next time you try to use it.
Use a retain to claim ownership of the NSString. Remember to release when you're done though (you can use properties to help you with this)
-(void)moveOneImageNewer{
int num = [numberOfImage intValue];
num--;
[numberOfImage release];
numberOfImage = [[NSString stringWithFormat:#"%i",num] retain];
//Load the image
[self loadImage];
}
-(void)moveOneImageOlder{
int num = [numberOfImage intValue];
num++;
[numberOfImage release];
numberOfImage = [[NSString stringWithFormat:#"%i",num] retain];
//Load the image
[self loadImage];
}
Add this in dealloc:
- (void)dealloc {
[numberOfImage release];
[super dealloc];
}
Well, the NSString class method "stringWithFormat" returns an autorelease NSString object if I'm right.
So the second call to your method would have numberOfImage pointing to nothing, as the autorelease NSString object it used to be pointing to has already been released and deallocated since you didn't retain it.
The part that is directly causing the crash is [numberOfImage intValue] when you call the method a second time, as you sending a message to an object (pointed to by numberOfImage) that no longer exist.
According to the leak instrument in XCode it's saying this line is giving a memory leak (100%)?
self.unsentPatients = [[NSMutableArray alloc] initWithArray:[defaults arrayForKey:UNSENT]];
I'm correctly releasing etc. on dealloc (which is definitely being ran) so I don't understand where I am going wrong?
It's only a small leak and Analysis doesn't come up with anything, but nonetheless it's still a leak.
Kind regards,
Dominic
There are many things wring with this code.
I'm assuming that the property is retaining the value, then you should not assign the value the way you are doing now, but more like:
NSMutableArray *temp = [[NSMutableArray alloc] initWithArray:[defaults arrayForKey:UNSENT]];
self.unsentPatients = temp;
[temp release], temp = nil;
or
self.unsentPatients = [[[NSMutableArray alloc] initWithArray:[defaults arrayForKey:UNSENT]] autorelease];
You should also avoid using the self. syntax in dealloc or init, which will call a mutator.
In multithreaded environment this could give problems.
So the correct dealloc would be:
- (void) dealloc {
[unsentPatients release], unsentPatients = nil;
[super dealloc][;
}
Hi I generally create objects of another classes. can you please tel me if this wil be in the auto release pool? or should we release it manually.
if you init copy or new them you'll have to deallocate them if you put an autorlease with the allocation then they will be autoreleased
for example
Foo *foo = [[Foo alloc] init]; //you'll have release it somewhere yourself
And
Foo *foo = [[[Foo alloc] init] autorelease];// this will be autreleased
The simple case is : if you use init, you are responsible for releasing it, either by calling release or by calling autorelease.
e.g.
NSString *myString = [NSString alloc] init]; // You need to release this
...
[myString release]; // Now it's released - don't use it again!
or if you are going give it to someone else
NSString *myString = [NSString alloc] init]; // This needs releasing
...
return [myString autorelease]; // You are finished with it but someone else might want it
However, there's a few other cases.
NSString *myString = [NSString stringWithFormat:#"hi"];
This object is in the autorelease pool already - don't release it!
NSString *secondString = [myString copy];
This object needs releasing - it is not autoreleased.
Rule of thumb : Anything with init, copy or new in the name - you made it, you release it. Anything else will be autoreleased.
I am developing an iphone app. Instruments reported a leaked object ServiceTypes. Below is the relevant code. Does anyone have any ideas? Thanks a lot for your help.
ServiceTypes *serviceTypes = [[ServiceTypes alloc] init];
if ([userConnection getServiceTypes:serviceTypes]) {
if ([serviceTypes.types length] > 0) {
NSArray *array = [[NSArray alloc] initWithArray:[serviceTypes.types componentsSeparatedByString: SERVICE_TYPE_DELIMITOR]];
serviceRequestTypes = [[NSMutableArray alloc] initWithArray:array];
[array release];
}
}
[[self typesTableView] reloadData];
[serviceTypes release];
It doesn't look like serviceTypes is being leaked. From the code you posted, serviceTypes is always released at the end of the method, and it doesn't appear to be retained anywhere in your sample. My question is: what happens inside getServiceTypes:. Does that method retain the serviceTypes parameter?
One more thing. If serviceRequestTypes is an instance variable (and it looks like it is), then you may be leaking memory by reassigning it without releasing the existing serviceRequestTypes object first. You should either rewrite serviceRequestTypes to be a property and use a synthesized accessor or make sure to release it every time before assigning. If its current value is nil, no big deal; the release message will simply be ignored. For example:
[serviceRequestTypes release];
serviceRequestTypes = [[NSMutableArray alloc] initWithArray:[serviceTypes.types componentsSeparatedByString:SERVICE_TYPE_DELIMITER]];