Question

I’ve got a class with two properties:

@interface Contact : NSObject {
    NSString *lastname;
    NSString *lastNameUpper;
}

I’ve declared lastname as a property (and synthesize it in the .m-file):

@property (nonatomic, retain) NSString *lastname;

However, I want to write my own method to access the lastNameUpper, so I declared a method:

- (NSString *) lastNameUpper;

and implemented it like this:

- (NSString *) lastNameUpper {
    if (!lastNameUpper) {
        lastNameUpper = [lastname uppercaseString];
    }
    return lastNameUpper;
}

This works all right, but as this is called quite often, a lot of temporary objects are called. Interestingly, the Instruments show a lot of “Malloc (4k)”, and the number increase each time lastNameUpper is accessed. I can also see that the memory is allocated in objc_retailAutoreleaseReturnValue.

As this was working fine before I converted my project to ARC, I’m assuming that I have to make some ARC specific additions to the method signature, but I can’t seem to be able to make it work.

Any suggestions?

Answer 1

Override the - (void)setLastname:(NSString*)aLastname method (created automatically by @synthesize lastname, and set lastNameUpper as in the existing method.

Now create a lastNameUpper property (and synthesize it):

@property (nonatomic, readonly) NSString *lastNameUpper;

Since this will return the pointer of the lastNameUpper instance variable, no copies should be made whenever this is accessed.