ios - NSComparisonResult 选项

Question

在我的 iOS 应用程序中，我实现了一个来自核心数据的表格 View 和一个搜索栏。在当前状态下，搜索只显示以搜索字符串开头的字段，但我想要的是显示包含至少三个字符长度的搜索文本的字段。

这是我的搜索功能代码:

- (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];
            }
        }
    }
}

恳请您教我如何根据需要进行搜索，任何字段的搜索字符串长度至少为三个字符。谢谢。

Answer 1

在我看来，最适合您要求的最简单方法是使用 NSPredicate 过滤出 [self.fetchedResultsController fetchedObjects] 数组并使用它。 NSPredicate 可以应用于任何 NSArray 以过滤掉其发送 filteredArrayUsingPredicate: 消息到该数组实例的结果。所以我的建议是使用如下代码:

-(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
    }]];
}