Does @"some text" give an autoreleased or retain 1 object back?

Question

Given this code:

// Initialize string
NSString *name = @"Franzi";

@"" macro creates a NSString with given text (here the name Franzi) and a RETAIN COUNT OF 1?

So @"" gives an NSString with have to be released or not? Am I responsible for this object? Second code example then confuses me, even though I am using it that way:

NSSting *message;
message = [NSString stringWithFormat:@"Hello @%!",name];
//message = [NSString stringWithFormat:@"Hello Girl!"];

So message gets released in next run loop, k. But what is with the NSString given as argument for stringWithFormat?

Does the class object NSString release the NSString @"Hello %@"/@"Hello Girl" given as arguement? Or does @""-Konstruktor only give back autoreleased NSStrings?

Answer 1

The NSString literal notation @"" gives you compile-time constant strings that reside in their own memory space and have constant addresses.

Contrary to popular belief, the reason why you don't release literal strings is not because they are part of the autorelease pool. They aren't — instead, they spend the entire application's lifetime in that same memory space they're allocated at compile time, and never get deallocated at runtime. They're only removed when the app process dies.

That said, the only time you need to memory-manage constant NSStrings is when you retain or copy them for yourself. In that case, you should release your retained or copied pointers, just like you do any other object.

Another thing: it's the literals themselves that don't need memory management. But if you pass them as arguments to NSString's convenience methods or initializers, like you do with stringWithFormat:, then it's those objects returned by the methods and initializers that follow all memory management rules normally.