CODEWITHSUNDEEP
objective-ciosmemory-managementmemory-leaksnsmutablearray
Anish
Anish

Reputation: 2917

Managing Memory in Objective c

I am doing my project in xcode 4.2 (Older Version). For my application, I just set the variables, arrays in dto class for using in entire app lifecycle. so I set with a property like this.

AppDTO(sub class of NSObject)

AppDTO.h

@property(nonatomic,retain)anotherAppDTO *aAppDTO;
@property(nonatomic,retain)NSMutableArray *array1;
@property(nonatomic,retain)NSMutableArray *array2;
@property(nonatomic,retain)NSString *string1,*string2,*string3;

AppDTO.m 

- (id)init
{
    self = [super init];
    if (self) {

    self.aAppDTO = [[anotherAppDTO alloc]init];
    self.array1 = [[NSMutableArray alloc]init];
    self.array2 = [[NSMutableArray alloc]init];

    self.string1 = @"Hello";
    self.string2= @"Hai";

    }
}


-(void)dealloc
{
    if(array1 != nil)
    {
        [array1 release];
        array1 = nil;
    }

    if(array2 != nil)
    {
        [array2 release];
        array2 = nil;
    }

    [aAppDTO release];
    aAppDTO = nil;

    [super dealloc];
}

when I analyze my app in Xcode 4.3.2, I get memory warning in self.array1 and self.array2 (Potential leak on object allocated on line….), but when I change self.array1 to array1, warning goes away.

What is the reason for using self. do I need to use self if I set @property(nonatomic,retain) to variables(like array1,array2,string1,string2).

Also in dealloc method, I heard we don't want to use [self.array1 release], instead we can use [array1 release]. Is it Correct?

Do I need to release my string in dealloc method.

Also I am releasing aAppDTO in dealloc method. if I allocate some objects in anotherAppDTO class, will it release automatically when I call [aAppDTO release] method.

Can anyone clarify me.

Many Thanks, Anish

Upvotes: 0

Views: 188

Answers (3)

Rob
Rob

Reputation: 437412

I think the others have answered your question.

I do want to draw your attention to Apple's excellent Advance Memory Management Programming Guide: Practical Memory Management, in which they walk through these sorts of scenarios. It's hard to take it all in on the first reading, but it really does cover this stuff. In answer to your question about the use of instance variables versus the accessor methods, I draw your attention to the section labeled to "Don't Use Accessor Methods in Initializer Methods and dealloc".

Upvotes: 0

aleroot
aleroot

Reputation: 72626

You get the warning because when you write : 

self.array1 = [[NSMutableArray alloc]init];

is the same as : 

[self setArray1: [[NSMutableArray alloc]init]];

As you can notice you are not allocating the underlying array1 private variable, but you are calling the setter of the property that since it is declared as retain it retains the object once assigned, this means that when you eventually will assign another object the second time with the setter the first object will remain with a retain count of one until the application will be closed (since you don't have any reference to that object anymore ...) .

Take a look at this great article to understand better Manual Reference Counting in Objective-C .

Upvotes: 4

justin
justin

Reputation: 104698

when i analyze my app in Xcode 4.3.2, i get memory warning in self.array1 and self.array2 (Potential leak on object allocated on line….), but when i change self.array1 to array1, warning goes away.

the analyzer's right. the parameter is retained when set. as well, you should favor direct access in initialization and dealloc. so, you should just write array1 = [[NSMutableArray alloc] init];, and be done.

What is the reason for using self. do i need to use self if i set @property(nonatomic,retain) to variables(like array1,array2,string1,string2).

those go through the accessor methods. if not in initialization or dealloc, you should favor going through the accessor methods because that is the common correct execution path for a fully constructed object.

Also in dealloc method, i heard we don't want to use [self.array1 release], instead we can use [array1 release]. Is it Correct?

correct.

Do i need to release my string in dealloc method.

yes.

Also I am releasing aAppDTO in dealloc method. if i allocate some objects in anotherAppDTO class, will it release automatically when i call [aAppDTO release] method.

when its reference count reaches 0, its dealloc will be called.

Upvotes: 2

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