Question

In ARC, does it create a memory leak to alloc into a @property (strong)

// MyClass.h
@property (strong) NSString *myString;

// MyClass.m
@synthesize myString=_myString;

- (void)viewDidLoad
{
    self.myString = [[NSString alloc] initWithFormat:@"Test %@", otherString];
}

I know that in manual memory management, the equivalent would create a leak

// MyClass.h
@property (retain) NSString *myString;

// MyClass.m
@synthesize myString=_myString;

- (void)viewDidLoad
{
    self.myString = [[NSString alloc] initWithFormat:@"Test %@", otherString];
}

- (void)dealloc
{
    [_myString release];
}

Is ARC able to handle the top example correctly? Does it optimize away one of the retains? Or maybe release twice in the dealloc?

Answer 1

This is perfectly valid under ARC.

I would recommend reading the ARC documentation to get more comfortable with trusting what it has to offer. http://clang.llvm.org/docs/AutomaticReferenceCounting.html and Mike Ash has a great blog post on how it works http://www.mikeash.com/pyblog/friday-qa-2011-09-30-automatic-reference-counting.html