Instance of method leaking, iPhone - iphone

Question

The following method shows up as leaking while performing a memory-leaks test with Instruments:
- (NSDictionary*) initSigTrkLstWithNiv:(int)pm_SigTrkNiv SigTrkSig:(int)pm_SigTrkSig SigResIdt:(int)pm_SigResIdt SigResVal:(int)pm_SigResVal {
NSArray *objectArray;
NSArray *keyArray;
if (self = [super init]) {
self.SigTrkNiv = [NSNumber numberWithInt:pm_SigTrkNiv];
self.SigTrkSig = [NSNumber numberWithInt:pm_SigTrkSig];
self.SigResIdt = [NSNumber numberWithInt:pm_SigResIdt];
self.SigResVal = [NSNumber numberWithInt:pm_SigResVal];
objectArray = [NSArray arrayWithObjects:SigTrkNiv,SigTrkSig,SigResIdt,SigResVal, nil];
keyArray = [NSArray arrayWithObjects:#"SigTrkNiv", #"SigTrkSig", #"SigResIdt", #"SigResVal", nil];
self = [NSDictionary dictionaryWithObjects:objectArray forKeys:keyArray];
}
return self;
}
code that invokes the instance:
NSDictionary *lv_SigTrkLst = [[SigTrkLst alloc]initSigTrkLstWithNiv:[[tempDict objectForKey:#"SigTrkNiv"] intValue]
SigTrkSig:[[tempDict objectForKey:#"SigTrkSig"] intValue]
SigResIdt:[[tempDict objectForKey:#"SigResIdt"] intValue]
SigResVal:[[tempDict objectForKey:#"SigResVal"] intValue]];
[[QBDataContainer sharedDataContainer].SigTrkLstArray addObject:lv_SigTrkLst];
[lv_SigTrkLst release];
Instruments informs that 'SigTrkLst' is leaking. Even though I have released the instance?
(I know that adding it to the array increments the retainCount by 1 but releasing it twice removes it from the array?)

Answer 1

You are initializing the instance (self), but then replacing it with a dictionary. Assuming that is what you actually want to do (see part 2), you need to release the old self before assigning a new one, and then you must retain the new dictionary so that your init method preserves the retain count. Note that this code returns a NSDictionary object, when your calling code expects a SigTrkLst, which is almost certainly a bad idea.
- (NSDictionary*) initSigTrkLstWithNiv:(int)pm_SigTrkNiv
SigTrkSig:(int)pm_SigTrkSig
SigResIdt:(int)pm_SigResIdt
SigResVal:(int)pm_SigResVal {
NSArray *objectArray;
NSArray *keyArray;
if (self = [super init]) {
self.SigTrkNiv = [NSNumber numberWithInt:pm_SigTrkNiv];
self.SigTrkSig = [NSNumber numberWithInt:pm_SigTrkSig];
self.SigResIdt = [NSNumber numberWithInt:pm_SigResIdt];
self.SigResVal = [NSNumber numberWithInt:pm_SigResVal];
objectArray = [NSArray arrayWithObjects:
SigTrkNiv,SigTrkSig,SigResIdt,SigResVal, nil];
keyArray = [NSArray arrayWithObjects:
#"SigTrkNiv", #"SigTrkSig", #"SigResIdt", #"SigResVal", nil];
[self release];
self = [NSDictionary dictionaryWithObjects:objectArray forKeys:keyArray];
[self retain];
}
return self;
}
Part 2: What is this supposed to do? Normally speaking, an -init... method should return an initialized class instance, starting from an allocated chunk of memory. The first part of your -init method looks right, other than the return value. For example, the following is a normal -init method:
- (id)initSigTrkLstWithNiv:(int)pm_SigTrkNiv
SigTrkSig:(int)pm_SigTrkSig
SigResIdt:(int)pm_SigResIdt
SigResVal:(int)pm_SigResVal {
if (self = [super init]) {
self.SigTrkNiv = [NSNumber numberWithInt:pm_SigTrkNiv];
self.SigTrkSig = [NSNumber numberWithInt:pm_SigTrkSig];
self.SigResIdt = [NSNumber numberWithInt:pm_SigResIdt];
self.SigResVal = [NSNumber numberWithInt:pm_SigResVal];
}
return self;
}

Answer 2

self = [NSDictionary dictionaryWithObjects:objectArray forKeys:keyArray];
When you are doing this what is happening to the SigTrkLst object that self supposed to point? Don't are you loosing reference to SigTrkLst object that was allocated and pointed by self? That object is never released as after this line there is no reference to that.
Though it is technically possible for an init method to return an object of different type, most probably this is not most of the people want and might indicate a potential bug.
EDIT: It seems that you are missing some basics of memory management for iOS. I strongly request you to read Memory Management Programming Guide. This may save you from lots of troubles.