CODEWITHSUNDEEP
objective-cmemory-managementmemory-leaksproperties
Java Ka Baby
Java Ka Baby

Reputation: 4920

Preventing leaks when using @property and @synthesize

What steps should we take -- what are the best practices -- to prevent leaks when using @property and @synthesize?

Upvotes: 0

Views: 259

Answers (2)

crackity_jones
crackity_jones

Reputation: 1077

Be aware of your standard things that give you back retained objects, methods with alloc, copy or new. When you invoke these along with your property you can inadvertently create a leak.

In your interface you have 

@property (nonatomic, retain) NSArray *someArray;

And in your implementation you have

@synthesize someArray;

Then later on you use the the property

self.someArray = [[NSArray alloc] init];

your object now has a retain count of 2. one from using self.someArray = and one from the alloc. self.someArray = invokes your setter which is the same as - (void)setSomeArray:(NSArray)someArray; which is created for you with the synthesize. This is going to contain a retain because of the retain keyword you used in the @property declaration.

I tend to avoid this one of two ways.

either with using the autoreleased intializer

self.someArray = [NSArray array];

or 

self.someArray = [[[NSArray alloc] init] autorelease];

or use a temp variable

NSArray tempArray = [[NSArray alloc] init];
self.someArray = tempArray;
[tempArray release];

all of these methods will leave you with your self.someArray object having a retain count of one which you can take care of in the dealloc.

- (void)dealloc {
[someArray release];
[super dealloc];
}

Upvotes: 3

Monolo
Monolo

Reputation: 18253

One thing that has helped me a lot is to check your header file for property definitions with a retain type, and then make sure that there is a release for each of them in the -dealloc method.

For the various assignments to the properties during the lifetime of the object, the automatic synthesized setters should take care of it.

Upvotes: 0

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