As @rmaddy already said in a comment, the decimal separator of NSNumberFormatter
is
locale dependent. If you have a fixed input format with the dot as decimal separator,
you can set the "POSIX locale":
NSNumberFormatter *myFormatter = [[NSNumberFormatter alloc] init];
[myFormatter setLocale:[NSLocale localeWithLocaleIdentifier:@"en_US_POSIX"]];
NSNumber *myNumber = [myFormatter numberFromString:@"42.00000"];
Alternatively, you can use NSScanner
to parse a double value, as e.g. described
here: parsing NSString to Double