Question

I have a question about a retain and a NSString, if I have a method who a return a NSString, and I put the return NSString in a nsstring variable, I must do a retain or not?

NSString *myString = @"";
myString = [self methodWhoReturnString]; // I must do this?
myString = [[self methodWhoReturnString]retain]; // Or I must do this?

Answer 1

The Apple Developer Documentation on Memory Management explains the scenarios where you retain/release objects.

Simply put, if you want the string to stick around, you need to retain it until you’re finished with it. If that is just the scope of the current function, you can get away without retaining it as if the string is already autorelease’d (likely) it won’t get released until your function finishes and the current AutoReleasePool is purged.

Bear in mind that an NSString * could actually be pointing to an NSMutableString *. If it matters to you if the string is changed by some other function without you realizing, be sure to copy it: NSString * myCopyOfString = [mystring copy];