CoreData 获取请求 - 复杂谓词

Question

我将如何使用（理想情况下）带有键值编码集合运算符的单个谓词来简化此过程？ （最后感兴趣的数组是filteredGames。）

NSManagedObjectContext *context;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:@"Game" inManagedObjectContext:context];
NSArray *games = [context executeFetchRequest:request error:nil];

NSMutableArray *filteredGames = [[NSMutableArray alloc] init];
for (Game *game in games) {
    NSInteger maxRoundNumber = [game.rounds valueForKeyPath:@"@max.number"];
    Round *maxRound = [[game.rounds filteredSetUsingPredicate:[NSPredicate predicateWithFormat:@"number = %d", maxRoundNumber]] anyObject];
    if (maxRound.someBoolProperty)
        [filteredGames addObject:game];
}

游戏有一个NSSet 属性rounds 和Rounds，并且Round 有一个NSInteger 属性number，我正在寻找那些Games 的最高编号Round 有一些BOOL 属性someBoolProperty。

Answer 1

这似乎是你想要的：

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Game"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY SUBQUERY(rounds, $r, $r.someBoolProperty = YES).number = @max.rounds.number"];