iPhone 'Whole Word' Search

Question

I am currently using the following algorithm to search on my iPhone app:

NSRange range = [entry.englishEntry rangeOfString:searchText options:NSCaseInsensitiveSearch];
  if(range.location != NSNotFound)
  {
   [self.filteredListContent addObject:entry];
        }

The problem is that when I search for a word like 'crap' I also get results for words like 'scrap' which is irrelevant. I am unfamiliar with NSRange so what is the search algorithm for searching the whole word?

Answer 1

Instead of finding the range of a string, just do a case-insensitive compare and check if the result is NSOrderedSame

if([entry.english caseInsensitiveCompare:searchText] == NSOrderedSame){
  [self.filteredListContent addObject:entry];
}

This will compare the text with the whole word and not just look for the range.

Answer 2

I just solved this problem by adding a simple category on NSString to do a word boundary search. Here's the code:

@interface NSString (FullWordSearch)

// Search for a complete word. Does not match substrings of words. Requires fullWord be present
// and no surrounding alphanumeric characters.
- (BOOL)containsFullWord:(NSString *)fullWord;

@end

@implementation NSString (FullWordSearch)

- (BOOL)containsFullWord:(NSString *)fullWord {
    NSRange result = [self rangeOfString:fullWord];
    if (result.length > 0) {
     if (result.location > 0 && [[NSCharacterSet alphanumericCharacterSet] characterIsMember:[self characterAtIndex:result.location - 1]]) {
      // Preceding character is alphanumeric
      return NO;
     }
     if (result.location + result.length < [self length] && [[NSCharacterSet alphanumericCharacterSet] characterIsMember:[self characterAtIndex:result.location + result.length]]) {
      // Trailing character is alphanumeric
      return NO;
     }
     return YES;
    }
    return NO;
}

@end

Answer 3

Yes you can search within words. You need to split the string into components first. Then loop through each one and compare them.

Something like that:

  NSArray *words = [entry.english componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
  for (NSString *word in words)
  { 
      NSComparisonResult result = [word compare:searchText options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch) range:NSMakeRange(0, [searchText length])];
      if (result == NSOrderedSame)
      {
        [self.filteredListContent addObject:entry];
        break;
      }
  }