objective-c - CoreData 获取请求 - 复杂谓词

Question

我如何使用(理想情况下)带有键值编码集合运算符的单个谓词来简化这个过程？ (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 Rounds，Round 有一个 NSInteger 属性 number，我正在寻找那些 Games，其最高编号 Round 具有一些 BOOL 属性someBoolProperty.

Answer 1

这似乎可以满足您的要求:

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