Memory management - Objective C.

[y2kreddy]

Hello, i have some memory issues in my program and i have the following questions.

question 1) i have a member variable of type nsstring and i dont have any property for it , i used it without self.xxx in various methods to access it. i have not allocated any memory for this variable and i need to know do i still have to release it in dealloc and assign nil in viewdidunload.

question 2)

i have a member variable with (nonatomic , retain) property. i have not used this vairable outside the class anywhere whatsoever. in order to use it within various methods of the class is it necessary for me to allocate memory for it or should it self.membervariable.

question 3) Do all iboutlet's with property(nonatomic,retain) require self.outlet=nil in viewdidunload and [outlet release]; in dealloc;

question 4) what about iboutlet's without property , do i have to do outlet=nil in viewdidunload and [outlet release]; in dealloc.

i gone through lot of memory management tutorials. the more i read the more i get confused. at last i have settled with 4 above questions i dont understand.if anyone could explain in 2 lines for each question that would be great. Thanks.

[baja_yu]

1. Depends on how you assign objects to the variable, but it's best to use properties so you don't have to manually manage it.
2. Allocation has to do with creation of an object, not use of a pointer variable, so I can't answer this really.
3. I generally just release IBOutlets in dealloc without setting them to nil
4. If it's without property then you must at least release it, setting it to nil will leak. It's best to use properties.

The best guide on Mem Management is the one in the documentation, by far. Here it is Loading…

[BrianSlick]

1. If there is no property, there is no rule. You will have to make decisions based on what you did elsewhere in code. Having consistent rules is one of the reasons to use properties. Also:

Release in dealloc - only for retain and copy properties.
Set to nil in viewDidUnload - only for IBOutlets and/or items that are created in viewDidLoad.

2. Declaring a property does not create an object. You will need to create one separately.

3. "Required" isn't the right word. If you don't release things in dealloc, then you will leak memory. If you don't nil out IBOutlets, then you are not reducing your memory usage as far as you could be. Those are consequences for failing to perform those actions. Is it "required" to put the toilet seat down? No. Will your wife chew on you if you fail to do so? Yes. Will life be easier for you if you just put it down? Yes.

4. Use properties for them, and then you don't have to worry about it.

[Meredi86]

Is it "required" to put the toilet seat down? No. Will your wife chew on you if you fail to do so? Yes. Will life be easier for you if you just put it down? Yes.

LOL Ah a smile on my face at the end of the week - thats rare!!

I would like to interject a little question here if i may? I have this method set up (works no issues just a mem management question):

- (void) ipCuIdCount {
    int n;
    int ipCuIdInt = 0;
    for (n = 0; n <= count; n = n + 1) {
        ipCuIdInt = n;
        //NSLog(@"the int: %i", ipCuIdInt);
        ipCuIdString = (NSString*)ipCuIdInt;
        //NSLog(@"HERE: %@", ipCuIdString);
    }
    
}

And in that method this is set up as a property like so:

@property (nonatomic, retain) NSString *ipCuIdString;

I release this in dealloc as i believe i should. the question comes with the use of "self" Brian has hinted to me in the past that if i do not "self." or [self var] then i will not be using the property correctly. So when i was messing with my code this morning i added self so the method looked like this:

- (void) ipCuIdCount {
    int n;
    int ipCuIdInt = 0;
    for (n = 0; n <= count; n = n + 1) {
        ipCuIdInt = n;
        //NSLog(@"the int: %i", ipCuIdInt);
        self.ipCuIdString = (NSString*)ipCuIdInt;
        //NSLog(@"HERE: %@", ipCuIdString);
    }
    
}

And this resulted in a crash every time i ran the code without fail (EXC_BAD_ACCESS) and Zombies wouldnt tell me what from. Would anyone be able to explain that to me as i dont really understand what was going on there.

thanks Joe

[BrianSlick]

Putting (NSString *) in front of an integer does not convert the integer into a string.

[Meredi86]

ok so because i am just casting it to the string rather than converting it if i force it into the property - a string then it doesnt like it? I think i get that, and may have to alter that method if i get a chance to make it a bit more robust.

thanks Brian

[BrianSlick]

self.ipCuIdString = [NSString stringWithFormat:@"%d", ipCuIdInt];

[Meredi86]

Awesome, thanks saves me digging through my code to find the line :P