NSComparisonResult選項

Question

在我的iOS應用程序中，我已經實現了核心數據和搜索欄的表格視圖。在當前狀態下，搜索僅顯示以搜索字符串開頭的字段，但我想要顯示包含至少三個字符長度的搜索文本的字段。

That's是我的搜索功能代碼：

- (void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope 
{ 
    NSLog(@"Previous Search Results were removed."); 
    [self.searchResults removeAllObjects]; 

    for (Person *person in [self.fetchedResultsController fetchedObjects]) 
    { 
     if ([scope isEqualToString:@"All"] || [person.firstname isEqualToString:scope]) 
     { 
      NSComparisonResult result = [person.firstname compare:searchText 
                options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch) 
                range:NSMakeRange(0, [searchText length])]; 
      if (result == NSOrderedSame) 
      { 
       NSLog(@"Adding person.firstname '%@' to searchResults as it begins with search text '%@'", person.firstname, searchText); 
       [self.searchResults addObject:person]; 
      } 
     } 
    } 
} 

請你們教我做搜索爲想要的方式，其中有至少三個字符的搜索字符串的任何領域長度。 謝謝。

Answer 1

最簡單的方法，最適合您的要求，我認爲是使用一個NSPredicate過濾掉[self.fetchedResultsController fetchedObjects]陣列和用它。 NSPredicate可以應用於任何NSArray，以過濾掉向該數組實例發送filteredArrayUsingPredicate:消息的結果。所以我的建議是使用一些類似於下面的代碼：

-(void)filterContentForSearchText:(NSString*)searchText scope:(NSString*)scope { 
self.searchResults = [[self.fetchedResultsController fetchedObjects] filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) { 
    Person* person = evaluatedObject; 
    NSString* firstName = person.firstname; 

    //searchText having length < 3 should not be considered 
    if (!!searchText && [searchText length] < 3) { 
     return YES; 
    } 

    if ([scope isEqualToString:@"All"] || [firstName isEqualToString:scope]) { 
     return ([firstName rangeOfString:searchText].location != NSNotFound); 
    } 
    return NO; //if nothing matches 
    }]]; 
} 

Answer 2

展開了討論至少，天真蠻力方法：

// get a set of all substrings; using a set means these will be deduplicated 
NSMutableSet *substrings = [NSMutableSet set]; 
for(NSInteger index = 0; index < searchText.length - 3; index++) 
    [substrings addObject:[searchText substringWithRange:NSMakeRange(index, 3)]]; 

// search every person for every single last possibility 
[self.searchResults removeAllObjects]; 
for(Person *person in [self.fetchedResultsController fetchedObjects]) 
{ 
    // ... scope and whatever else tests here ... 

    for(NSString *string in substrings) 
    { 
     if([person.firstname rangeOfString:string].location != NSNotFound) 
     { 
      [self.searchResults addObject:person]; 
      break; // exit the string in substrings loop early 
     } 
    } 
}