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;
}