objective-c - NSPredicate 连接属性

Question

我正在尝试弄清楚如何连接属性名称。我有一个县和一个地区属性，我想像这样查询

[NSPredicate predicateWithFormat:@"county + district contains[cd] %@",searchBar.text]

为谓词错误提供未实现的 SQL 生成。而且我不确定如何实现 NSPredicate。谢谢

Answer 1

这应该让您了解如何进行更复杂的搜索。它将匹配“县区”、“区县”等查询。

    NSArray *searchTerms = [searchBar.text componentsSeparatedByString:@" "];
    NSString *predicateFormat = @"(county contains[cd] %@) OR (district contains[cd] %@)";
    NSPredicate *predicate;
    if ([searchTerms count] == 1) {
        NSString *term = [searchTerms objectAtIndex:0];
        predicate = [NSPredicate predicateWithFormat:predicateFormat, term, term];
    } else {
        NSMutableArray *subPredicates = [NSMutableArray array];
        for (NSString *term in searchTerms) {
            NSPredicate *p = [NSPredicate predicateWithFormat:predicateFormat, term, term];
            [subPredicates addObject:p];
        }
        predicate = [NSCompoundPredicate andPredicateWithSubpredicates:subPredicates];
    }
    [fetchRequest setPredicate:predicate];

参见 Cocoa Is My Girlfriend: Adding iTunes-style search to your Core Data application以获得更多解释。