核心数据谓词“无法解析格式字符串”

Question

我正在尝试获取一组与其他对象具有特定关系的NSManagedObjects。

所以我有 4 个托管对象：UserPick、Game、Group、User。 UserPick 分别与Game、Group、User 具有一对一的关系。我需要找到所有具有特定Game、Group 和User 的UserPicks，但我似乎无法正确构建谓词：

我试过了：

[NSPredicate predicateWithFormat:@"%K = %@, %K = %@, %K = %@",
UserPickRelationships.game, game,
UserPickRelationships.group, group,
UserPickRelationships.user, user]

和：

[NSPredicate predicateWithFormat:@"%K = %@, %K = %@, %K = %@",
UserPickRelationships.game, game.objectID,
UserPickRelationships.group, group.objectID,
UserPickRelationships.user, user.objectID]

终于：

[NSPredicate predicateWithFormat:@"%K.%K = %@, %K.%K = %@, %K.%K = %@",
UserPickRelationships.game, @"objectID", game.objectID,
UserPickRelationships.group, @"objectID", group.objectID,
UserPickRelationships.user, @"objectID", user.objectID]

我已经尝试在所有可能的组合中使用%@ 和%K。我得到的只是：NSPredicate cannot parse format string。我怎样才能做到这一点？

Answer 1

您可能希望将条件与“AND”结合起来：

[NSPredicate predicateWithFormat:@"%K = %@ AND %K = %@ AND %K = %@",
UserPickRelationships.game, game,
UserPickRelationships.group, group,
UserPickRelationships.user, user]

（假设UserPickRelationships.game 计算结果为字符串"game"）。