Word Stemming in iOS - Not working for single word

Question

I am using NSLinguisticTagger for word stemming. I am able to get a stem words of words in a sentence, but not able to get a stem word for a single word.

Following is the code I am using,

    NSString *stmnt = @"i waited";
    NSLinguisticTaggerOptions options = NSLinguisticTaggerOmitWhitespace | NSLinguisticTaggerOmitPunctuation | NSLinguisticTaggerJoinNames;

    NSLinguisticTagger *tagger = [[NSLinguisticTagger alloc] initWithTagSchemes:@[NSLinguisticTagSchemeLemma] options:options];
    tagger.string = stmnt;
    [tagger enumerateTagsInRange:NSMakeRange(0, [stmnt length]) scheme:NSLinguisticTagSchemeLemma options:options usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) {
        NSString *token = [stmnt substringWithRange:tokenRange];
        NSLog(@"%@: %@", token, tag);
    }];

For this I am getting out correctly as:

i: i
waited: wait

But the above code fails to identify stem word if stmnt = @"waited";

Any help is greatly appreciated

Answer 1

Following code worked for me,

NSString *stmt = @"waited";
NSRange stringRange = NSMakeRange(0, stmt.length);
NSDictionary* languageMap = @{@"Latn" : @[@"en"]};
[stmt enumerateLinguisticTagsInRange:stringRange
                                       scheme:NSLinguisticTagSchemeLemma
                                      options:NSLinguisticTaggerOmitWhitespace
                                  orthography:[NSOrthography orthographyWithDominantScript:@"Latn" languageMap:languageMap]
                                   usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) {
                                       // Log info to console for debugging purposes
                                       NSString *currentEntity = [stmt substringWithRange:tokenRange];
                                       NSLog(@"%@ is a %@, tokenRange (%d,%d)",currentEntity,tag,tokenRange.length,tokenRange.location);
                                   }];