iOS Memory Management & NSString Initialisation - ios

Question

Still learning iOS development with ObjectiveC and iOS, and trying to realy understand memory management! Appreciate any advise on the snippet below, eg:
1) Analyser says there are potential memory leaks, but can't solve them?
2) Should I keep alloc and init the NSStrings in the for loop and when appended to?
Thanks
- (NSString *) lookUpCharNameForID: (NSString *) inCharID
{
debugPrint ("TRACE", [[#"Lookup Char Name for = " stringByAppendingString: inCharID] UTF8String]);
NSString *tempName = [[NSString alloc] initWithFormat: #""];
if (![inCharID isEqualToString: #""])
{
// Potentially lookup multiple values
//
NSString *newName = [[NSString alloc] initWithFormat: #""];
NSArray *idList = [inCharID componentsSeparatedByString: #","];
for (NSString *nextID in idList)
{
NSLog( #"Lookup %i : %#", [idList count], nextID);
newName = [[NSString alloc] initWithFormat: #"C%#", nextID];
// Append strings
if ([tempName isEqualToString: #""])
tempName = [[NSString alloc] initWithFormat: #"%#", newName];
else
tempName = [[NSString alloc] initWithFormat: #"%#+%#", tempName, newName];
}
[newName release];
}
return [tempName autorelease];
}

Answer 1

You don't need any of the calls to alloc, release, or autorelease. Instead, use [NSString stringWithFormat:] to create instances of NSString that you don't own, and therefore don't need to manage. Also, consider using NSMutableString to simplify your code a bit, for example along the lines of the following (untested) version:
- (NSString *) lookUpCharNameForID: (NSString *) inCharID
{
NSMutableString *tempName = nil;
if (![inCharID isEqualToString: #""])
{
NSArray *idList = [inCharID componentsSeparatedByString: #","];
for (NSString *nextID in idList)
{
[tempName appendString:#"+"]; // Does nothing if tempName is nil.
if (tempName == nil)
tempName = [NSMutableString string];
[tempName appendFormat:#"C%#", nextID];
}
}
return tempName;
}

Answer 2

You have 2 alloc initWithFormat for tempName. One before the loop and one within the loop.

Answer 3

Use ARC (Automatic Reference Counting) for new projects. For older projects it may be easy to convert them, if not ARC can be disabled on a file-by-file basis where necessary.
Using a mutable string, autoreleased convience methods and a little rerfactoring:
- (NSString *) lookUpCharNameForID: (NSString *) inCharID
{
NSMutableString *tempName = [NSMutableArray array];
if (inCharID.length)
{
NSArray *idList = [inCharID componentsSeparatedByString: #","];
for (NSString *nextID in idList)
{
if (tempName.length == 0)
[tempName appendFormat: #"%#C", nextID];
else
[tempName appendFormat: #"+%#C", nextID];
}
}
return tempName;
}