Question

Here’s a piece of code to take a string (either NSString or NSAttributedString) input that represents a command line and parse it into two strings, the command cmd and the arguments args:

NSString* cmd = [[input mutableCopy] autorelease]; NSString* args = [[input mutableCopy] autorelease]; NSScanner* scanner = [NSScanner scannerWithString:[input string]]; [scanner scanUpToCharactersFromSet:[NSCharacterSet                                      whitespaceAndNewlineCharacterSet]                          intoString:&cmd]; if (![scanner scanUpToString:@'magicstring666' intoString:&args]) args = @''; 

That seems to work but the magic string is a pretty absurd hack. Also, I’m not at all sure I’m doing things right with the autoreleases.

ADDED: The solution should also be robust to initial whitespace. Also, I originally had the input string called both input and inStr. Sorry for that confusion.

ADDED: I believe one thing the above code gets right that the answers so far don’t is that args should not have any initial whitespace.

Answer 1

NSString *cmd; NSScanner *scanner = [NSScanner scannerWithString:[inStr string]]; [scanner scanUpToCharactersFromSet:[NSCharacterSet                                     whitespaceAndNewlineCharacterSet]                          intoString:&cmd]; NSString *args = [[scanner string] substringFromIndex:[scanner scanLocation]]; 

Your autoreleases were OK, but allocating strings in the first place was unnecessary since NSScanner returns a new string by reference. Since NSScanner’s charactersToBeSkipped include whitespace by default, it shouldn’t get tripped up by initial whitespace.