获得时的iOS NSLinguisticTagger总是返回null引理干

Question

我需要一个关键字（这是它的词汇形式）与文本匹配，返回是否关键字匹配（就像一个搜索引擎）

例如

text: I want some apples 
keyword: apple 
result: matched 
keyword: banana 
result: not matched 

这是我的方法，我总是空的标签

- (BOOL)matchKeywordWithText:(NSString *)text keyword:(NSString *)keyword { 

    __block NSMutableArray *words = [NSMutableArray array]; 


    NSLinguisticTaggerOptions options = NSLinguisticTaggerOmitWhitespace | NSLinguisticTaggerOmitPunctuation | NSLinguisticTaggerJoinNames; 
    NSLinguisticTagger *tagger = [[NSLinguisticTagger alloc] initWithTagSchemes: [NSLinguisticTagger availableTagSchemesForLanguage:@"en"] options:options]; 
    tagger.string = text; 
    [tagger enumerateTagsInRange:NSMakeRange(0, [text length]) scheme:NSLinguisticTagSchemeLemma options:options usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) { 
     NSString *token = [text substringWithRange:tokenRange]; 

     //TODO: TAG IS ALWAYS NULL HERE 
     NSLog(@"words are %@: %@", token, tag); 

     if (tag.length > 0) { 
      [words addObject:tag]; 
     } 
    }]; 

    for (NSString *word in words) { 
     if ([word isEqualToString:keyword]) { 
      return YES; 
     } 
    } 

    return NO; 

} 

Answer 1

下面的代码工作：

NSLinguisticTagger *tagger = [[NSLinguisticTagger alloc] 
           initWithTagSchemes:[NSArray arrayWithObjects:NSLinguisticTagSchemeNameTypeOrLexicalClass, NSLinguisticTagSchemeLemma, nil] 
           options:(NSLinguisticTaggerOmitWhitespace | NSLinguisticTaggerOmitPunctuation)]; 
NSString *text = @"i'm apples"; 
[tagger setString:text]; 
[tagger enumerateTagsInRange:NSMakeRange(0, [text length]) 
         scheme:NSLinguisticTagSchemeNameTypeOrLexicalClass 
        options:(NSLinguisticTaggerOmitWhitespace | NSLinguisticTaggerOmitPunctuation) 
        usingBlock:^(NSString *tag, NSRange tokenRange, NSRange sentenceRange, BOOL *stop) { 
         NSString *token = [text substringWithRange:tokenRange]; 

         NSString *lemma = [tagger tagAtIndex:tokenRange.location scheme:NSLinguisticTagSchemeLemma tokenRange:NULL sentenceRange:NULL]; 
         if (lemma == nil) { 
          lemma = token; 
         } 

         NSLog(@"%@, %@", token, lemma); 
        }];