Question

I am creating a calculator app and this is my first ios app, so i did not care much about memory management, but now that I look back I see some leaks. I know exactly where the leaks are(used Leaks – XCODE), as all the leaks are caused by NSStrings which cannot be modified. Hence, I have been allocating strings even for changing the text of the label:

label.text = [[NSString alloc] initWithFormat: @"%@", number];

where number is another string(which i have to modify a lot and again causing leaks)
Hence, everytime I modify the label, I have a leak.

Can someone please suggest what datatype to use so that I can just use one copy of the object and keep modifying it as I need. OR another way to change the label,number either w/o using alloc or releasing it in time.

I have tried autoreleasing it but it crasehes the app. FYI, along with the leaks, the app works great :)(but i know its wrong, hence)

Please help! Thank You

Answer 1

Assuming your label is UILabel, then your problem is obvious, the text property of UILabel is defined as retain, when you do an alloc it returns an object with retain +1 when you assign to the property the setter increases the retain count by one, therefore you have a +2 retain count, and when u get rid of your label you leak, the thing should look like

label.text = [[[NSString alloc] initWithFormat: @"%@", number] autorelease]; 

or

label.text = [NSString stringWithFormat: @"%@", number];

You should read up on memory managment guidelines here

-Daniel