I am using the code below to set my two NSArray ivars:
The issue is, I keep getting a memory leak on the following lines:
followingFriendsArray = [[NSArray alloc] initWithArray:friend.Following];
followerFriendsArray = [[NSArray alloc] initWithArray:friend.Followers];
Is this not the correct way to set ivars from an existing NSArray of items? Any help would be appreciated. I've also tried to autorelease the above two lines, but when I actually access them in another method I get an error that they've already been released.
I have included my Interface and Implementation code below:
Interface .h:
NSArray *followingFriendsArray;
NSArray *followerFriendsArray;
#property (nonatomic, retain) NSArray *followingFriendsArray;
#property (nonatomic, retain) NSArray *followerFriendsArray;
Implementation .m:
- (void)handlerGetFollowingInformation:(id)value {
BOOL success = [Utility checkWebServiceErrors:value controller:self.navigationController];
if (success) {
Friend *friend = (Friend *)value;
followingFriendsArray = [[NSArray alloc] initWithArray:friend.Following];
followerFriendsArray = [[NSArray alloc] initWithArray:friend.Followers];
}
}
This is how I need to access the arrays:
- (void)followersButtonTapped:(id)sender {
FollowingVC *fvc = [[FollowingVC alloc] initWithNibName:#"FollowingViewController" bundle:nil];
fvc.friends = followerFriendsArray;
[self.navigationController pushViewController:fvc animated:YES];
[fvc release];
}
I release my two ivars in the following way as per usual:
- (void)viewDidUnload {
self.followingFriendsArray = nil;
self.followerFriendsArray = nil;
[super viewDidUnload];
}
- (void)dealloc {
[followingFriendsArray release];
[followerFriendsArray release];
[super dealloc];
}
I mean the code works just fine, it's just that I'm concerned about said memory leaks when I run the "Leaks" performance tool.
OK
you should not use autorelease in this case, but you have to release the arrays by calling :
[followingFriendsArray release];
[followerFriendsArray release];
you can do it:
when you don't need to use them any more.
in the dealloc method in your .m file.
option 2looks like that -
- (void)dealloc {
[followingFriendsArray release];
[followerFriendsArray release];
[super dealloc];
}
BTW -
if you don't manipulate the arrays after creating them (add / remove objects) you should use an immutable array (NSArray).
Good Luck
Your method handlerGetFollowingInformation is assigning new values to followingFriendsArray and followerFriendsArray without releasing the previous contents. If you call this method more than once on the same instance you will leak.
CRD is right that the arrays are not released inside the handlerGeFollowingInformation method but the fix is maybe overkill. What you need to do is to use self. so that the setter method is called which does that automatically. You could should look like this:
- (void)handlerGetFollowingInformation:(id)value {
BOOL success = [Utility checkWebServiceErrors:value controller:self.navigationController];
if (success) {
Friend *friend = (Friend *)value;
self.followingFriendsArray = [[NSArray alloc] initWithArray:friend.Following];
self.followerFriendsArray = [[NSArray alloc] initWithArray:friend.Followers];
}
}
Easy fix but hard to spot and I ran into this issue over and over again especially when I started to dealloc are the properties.
-Andy
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 simple question. This is my header file :
#import <UIKit/UIKit.h>
#interface FirstFaceController : UIViewController
#property (nonatomic,retain) NSMutableDictionary *face1Layers;
#end
This .m, here i init my Dictionary and put where UIImageView :
#import "FirstFaceController.h"
#implementation FirstFaceController
#synthesize face1Layers;
-(void) dealloc {
[face1Layers release];
[super dealloc];
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.face1Layers = [NSMutableDictionary dictionary];
[self.face1Layers setObject:
[[UIImageView alloc] initWithImage:[UIImage imageNamed:#"pic.png"]]
forKey:#"pic"];
[self.view addSubview:[self.face1Layers objectForKey:#"pic"]];
if ( [[face1Layers objectForKey:#"pic"] superview] == nil ) {
//....
}
}
Then i call [[face1Layers objectForKey:#"pic"] superview] i have "EXC_BAD_ACCESS".
Why?
Try to do this:
NSMutableDictionary* tempDict = [[NSMutableDictionary alloc] init];
self.face1Layers = tempDict;
UIImageView* picView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"pic.png"]];
[self.face1Layers setObject:picView forKey:#"pic"];
[picView release];
[tempDict release];
Do not create and insert yours NSMutableDictionary and UIImageView throught a single line of code because you have leaks.
In the first case, if you do the following you have a retain count of two. face1Layers has a retain policy.
self.face1Layers = [[NSMutableDictionary alloc] init];
You can avoid this splitting the code as I explained before or send an autorelease message to the initialized object.
In the second case, when you add an object in NSDictionary or NSArray (and theirs subclasses), these classes retain added objects.
Hope it helps.
Well, I think there are a couple of things wrong here:
You never allocate the dictionary as in NSMutableDictionary alloc init
The UIImageView is allocated but never released. I would allocate before setting it as object, and then add it, and then release it
Got this code in my controllers (void)viewDidLoad method
self.purchasesPerClassification = [NSMutableDictionary
dictionaryWithObjects:[NSArray arrayWithObjects:#"Moo",nil]
forKeys:[NSArray arrayWithObjects:#"MooKey",nil]
];
as far I can under stand these are auto release as I have not used alloc init,
and in my dealloc i have
[self.purchasesPerClassification release];
this is part of a controller with UITableViewController and this controller is created an loaded from a main container and added to the main contollers navigationController this seems to make my app crash in the simulator as when I dont have it in the code it works fine any pointers on why this is crashing
heres the .h
#interface FirstAiderInsurancePurchasesViewController : UITableViewController {
NSArray * availableClassifications;
NSMutableDictionary * purchasesPerClassification;
}
#property(nonatomic, retain) NSArray * availableClassifications;
#property(nonatomic, retain) NSMutableDictionary * purchasesPerClassification;
#end
and heres the .m parts
#implementation FirstAiderInsurancePurchasesViewController
#synthesize availableClassifications;
#synthesize purchasesPerClassification;
- (void)viewDidLoad {
[super viewDidLoad];
self.availableClassifications = [NSMutableArray arrayWithObjects:#"Completed",#"Recover's",nil];
self.purchasesPerClassification = [NSMutableDictionary dictionaryWithObjects:[NSArray arrayWithObjects:#"Object",nil]
forKeys:[NSArray arrayWithObjects:#"ObjectKey",nil]];
}
- (void)dealloc {
[super dealloc];
self.availableClassifications = nil;
self.purchasesPerClassification = nil;
}
I've tried both
[purchasesPerClassification release];
as well and its crashing when I go back to the root controller
Firstly, what is the property definition of purchasesPerClassification?
Anyway, assuming it's copy or retain, you probably want either:
self.purchasesPerClassification = nil;
or
[purchasesPerClassification release];
[NSMutableDictionary dictionaryWithObjects] return an autoreleased instance
you have not to [self.purchasesPerClassification release];
but [purchasesPerClassification release]
Hi all i'm still new to iPhone development, but had strong experience with other programming languages. The thing that makes me pull my hair out is the Obj-C memmory management and releasing / retaining properly. I know the concept, i know "once i understand it will be easy" but i'm not quite still there, and that makes me crazy. Here i have one simple piece of code with class and method, that simply add's one character to existing string that is synthesized so used as class proprety ... the class for example is called myClass ...
myClas.h
#interface myClass : NSObject {
#private
NSString* someCommonString;
}
#propery (retain, nonatomic) NSString* someCommonString;
myClass.m
...
#synthesize someCommonString;
- (id) init
{
self = [super init];
if(self)
{
someCommonString = [[NSString alloc] initWith String:#"one "];
}
}
- (NSString*) appendString:(NSString*) stringToAdd
{
NSString* result = [someCommonString stringByAppendingString: stringToAdd];
return result;
}
- (void) doTheJob
{
NSString* test1 = #"two ";
NSString* test2 = [[NSString alloc] initWithString: #"three "];
NSString* test3 = [NSString stringWithFormat:#"four "];
self.someCommonString = [self appendString:test1];
self.someCommonString = [self appendString:test2];
self.someCommonString = [self appendString:test3];
NSLog(#"%#", someCommonString);
}
- (void) dealloc
{
[someCommonString release];
[super release];
}
...
Ok, after i alloc myClass and execute the doTheJob method, i should have #"one two three four" in the someCommonString class proprety. I know this is working, but is also leaking as hell. test1, test2 and test3 are 3 ways of initialising NSString, and only the test2 should be released, this is quite self-explanatory, but im much more worried what happens when passing them as arguments to the appendString method. Because there i know i hawe a leak, but don't know how to handle 1. stringToAdd argument [should i worry about it in appendString method at all ?] 2. the result -> if i autorelease the result, i don't know at which point the result will be deallocated. 3. sommeCommonString in appendStringMethod, should i retain it, release it or leave it alone ?
Huh :)
At a first glance, it seems to me like you're not releasing test2. After you have appended it to your common string, you do not need to retain it anymore.
self.someCommonString = [self appendString:test1];
self.someCommonString = [self appendString:test2];
self.someCommonString = [self appendString:test3];
[test2 release];
The other two (test1 and test3) are autoreleased, so your thread will reclaim them at some point).
As far as your appendString: method is concerned, result is already autoreleased and in fact you could reduce your implementation to
return [someCommonString stringByAppendingString: stringToAdd];
someCommonString is not affected by the operation at all. stringByAppendingString: returns a new autoreleased string from the concatenation of self and stringToAdd.
Hope that helps
… but im much more worried what happens when passing them as arguments to the appendString method. Because there i know i hawe a leak, but don't know how to handle
1. stringToAdd argument [should i worry about it in appendString method at all ?] …
You don't have a leak in -appendString:. You are passing stringToAdd around without retaining it and that's okay here.
The result is autoreleased and you don't have to take any action on it.
2. the result -> if i autorelease the result, i don't know at which point the result will be deallocated.
The result is already autoreleased and will be released as soon as the current NSAutoreleasePool will be released. Til then you can pass it around without retaining.
3. sommeCommonString in appendStringMethod, should i retain it, release it or leave it alone ?
Leave it alone, it's managed by the accessors. But as fedmest (and you too) said: release test2.
Well there are few problems in your code, but basic problem is you need NSMutableString string, not NSString to make your code work.
in init method, correct code to initialize is,
someCommonString = [[NSMutableString alloc] initWithString:#"one "];
You have to return the object (self) from init, otherwise it will not work, like this.
return self;
If you wanted to append the string, it should be NSMutableString, not NSString.
[[self someCommonString] appendString:test1];
[[self someCommonString] appendString:test2];
[[self someCommonString] appendString:test3];
In dealloc method, you call dealloc method of super, not release the super. So correct it it like this.
[super dealloc];
There is no need to release test1 and test3, because they are autorelease.
I have witten the correct code, try this out.
#interface myClass : NSObject {
#private
NSMutableString* someCommonString;
}
#property (retain, nonatomic) NSMutableString* someCommonString;
- (void) doTheJob;
#end
#implementation myClass
#synthesize someCommonString;
- (id) init
{
self = [super init];
if(self)
{
someCommonString = [[NSMutableString alloc] initWithString:#"one "];
}
return self;
}
- (NSString*) appendString:(NSString*) stringToAdd
{
NSString* result = [someCommonString stringByAppendingString: stringToAdd];
return result;
}
- (void) doTheJob
{
NSString* test1 = #"two ";
NSString* test2 = [[NSString alloc] initWithString: #"three "];
NSString* test3 = [NSString stringWithFormat:#"four "];
[[self someCommonString] appendString:test1];
[[self someCommonString] appendString:test2];
[[self someCommonString] appendString:test3];
NSLog(#"%#", someCommonString);
[test2 release];
}
- (void) dealloc
{
[someCommonString release];
[super dealloc];
}
#end
This is a technique which might help you deal better with what is happening with the #synthesize directive. Change your header as follows
#interface myClass : NSObject {
#private
NSString* _bob;
}
#property (retain, nonatomic) NSString* someCommonString;
and your class file to
#synthesize someCommonString = _bob;
If you recompile your code you will get build errors. Fix these and you will suddenly be able to see exactly what you are accessing via the synthesized property and what you are directly accessing.
Additionally, as already mentioned, you need to release test2 in the doTheJob method.
I've spent a couple of days trying to find out what's going on. I have read loads of Memory Management documentation and I am sick to death of hearing "for every alloc you need a release" - I know that and I still can't figure out why my code is producing memory leaks.
I am writing a simple custom class with an NSMutableDictionary as one of its properties. Basically it mimics an XMLELement. I cannot for the life of me figure out why the allocation of a dictionary is causing a memory leak. The leak occurs on the device as well as the simulator - 5 leaks on the device, and 20 on the simulator.
The leak occurs when I declare and allocate the variable *tmp.
There is also a leak when I set the attribute details (name and value).
This is driving me nuts. Please help!
Part of the code:
#interface IMXMLElement : NSObject {
NSString *strElementName;
NSString *strElementValue;
NSMutableDictionary *dictAttributes;
}
#property (nonatomic, retain) NSString *strElementName;
#property (nonatomic, retain) NSString *strElementValue;
#property (nonatomic, retain) NSMutableDictionary *dictAttributes;
#end
#implementation IMXMLElement
#synthesize strElementName;
#synthesize strElementValue;
#synthesize dictAttributes;
-(id)initWithName:(NSString *)pstrName
{
self = [super init];
if (self != nil)
{
self.strElementName = pstrName;
**LEAK NSMutableDictionary *tmp = [[NSMutableDictionary alloc] init];
self.dictAttributes = tmp;
[tmp release];
}
return self;
}
-(void)setAttributeWithName:(NSString *)pstrAttributeName
andValue:(NSString *)pstrAttributeValue
{
**LEAK [self.dictAttributes setObject:pstrAttributeValue forKey:pstrAttributeName];
}
-(void)dealloc
{
[strElementName release];
[strElementValue release];
[dictAttributes release];
[super dealloc];
}
The access this class using the following code:
NSString *strValue = [[NSString alloc] initWithFormat:#"Test Value"];
IMXMLElement *xmlElement = [[IMXMLElement alloc] initWithName:#"Test_Element"];
[xmlElement setAttributeWithName:#"id" andValue:strValue];
When you have strings as properties, declare them as copy, not retain.
NSMutableDictionary *tmp = [[NSMutableDictionary alloc] init];
self.dictAttributes = tmp;
[tmp release];
the above is unnecessary, instead do:
(retain count will automatically be incremented for this autorelease object)
self.dictAttributes = [NSMutableDictionary dictionaryWithCapacity:0];
in dealloc do:
(retain count will automatically be decremented)
self.dictAttributes = nil;
normally for properties you just set them to nil instead of explicitly releasing them
since the get/setter handles that for you.
Try [dictAttributes removeAllObjects] before releasing dictAttributes.
Edit:
Also, you will positive allocation because you are allocating memory for "tmp". The memory will be retained because you now have a reference from dictAttributes.
You then have more positive allocation when you add elements to the dictionary, which also need to be allocated and are kept in memory by the dictionary's internal references
Typical syntax is NSMutableDictionary *tmp = [[[NSMutableDictionary alloc] init] autorelease];