Re: Searching for "whole word" in NSString

FROM : Mike Wright
DATE : Tue Jan 29 21:28:46 2008

On Jan 29, 2008, at 10:12:21 -0800, John Stiles <<email_removed>> 
wrote:

> I'm trying to find a substring in an NSString. But I want to find 
> whole
> words (e.g. like in the Find panel when you choose "Full word" from 
> the
> popup, rather than "Contains" or "Starts With").
>
> Unless I'm missing something, it looks like NSString's
> -rangeOfString:options:range:locale: doesn't have an option for 
> finding
> whole words.
>
> How does the Find panel do it, then? Am I going to have to "roll my 
> own"
> code for string searching? That sounds error-prone to me; I'd much
> rather have the OS do it.


Here's a Tiger approach that's worked pretty well for me (or, at 
least, no non-English-using customers have complained--so far).

NSString *fieldContent; // the string I'm searching in
NSString *targetString; // the string to be found
NSRange hitRange; // the range of targetString found within fieldContent
NSRange testRange; // in the beginning, this covers all of fieldContent
BOOL caseSensitive; // specified by the user
BOOL isWholeWord = NO; // this is used in two sequential tests

// set up the search mask
unsigned searchMask = NSLiteralSearch;
if (! caseSensitive)
   searchMask |= NSCaseInsensitiveSearch;

// set up the character set for words
NSCharacterSet *wordCharacterSet = [NSCharacterSet 
alphanumericCharacterSet];

// look for targetString in fieldContent
hitRange = [fieldContent rangeOfString:targetString options: 
searchMask range:testRange];

// if we found something, do the whole-word test
if (hitRange.location != NSNotFound)
{
   // test the beginning of targetString
   isWholeWord = ((hitRange.location == 0) || (! [wordCharacterSet 
characterIsMember:[fieldContent characterAtIndex:(hitRange.location - 
1)]]));

   // if the beginning is okay, test the end of targetString
   if (isWholeWord)
   {
       unsigned nextCharPosition = hitRange.location + hitRange.length;
       isWholeWord = ((nextCharPosition == [fieldContent length]) || (! 
[wordCharacterSet characterIsMember:[fieldContent 
characterAtIndex:nextCharPosition]]));
   }
}

Finally:

if (isWholeWord)
{
   // show it to the user
}

Hope this helps. (And, since it's not just copied from my own code, I 
hope it doesn't contain any serious errors.)

Regards,
Mike Wright
http://www.idata3.com/
http://www.raccoonbend.com/