Question

   NSString *string=[temp objectAtIndex:row];
   [temp removeObjectAtIndex:row];

The object from which string is created no longer exists; I assume this syntax is straight assignment, thus string should no longer exist, right?

So either I’d use stringWithFormat to create a new string from the object, or send retain to string to be safe, is this correct reasoning?

Answer 1

Assuming you aren’t using ARC or garbage collection, yes, your reasoning about the object’s memory management is correct†. However, you wouldn’t want to use stringWithFormat:. That expects a format string, and it can fail horribly if you pass something that isn’t specifically meant to be one. You could use one of:

• stringWithString: if you don’t want ownership

• copy if you just want to make sure you have a safe reference to the string (optionally with autorelease if you don’t plan on keeping the reference around long-term)

• retain if you definitely want to keep the same object — even if it’s a mutable string — and do want ownership (You probably don’t want this option, as the main difference from copy is that the string could potentially mutate underneath you)

^{† By “correct”, I mean you’re right that you shouldn’t assume anything about the object’s lifecycle beyond that point. It might still be alive, but it’s technically not a safe assumption. Thought it worth mentioning because some people aren’t 100% clear on this point.}