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;
}