我有这个位来检索两个用户之间的所有消息:letuser1="john"letuser2="mark"letpredicateUser1To2=NSPredicate(format:"user1==%@",user1)letpredicateUser2From1=NSPredicate(format:"user2==%@",user2)letpredicateUser2To1=NSPredicate(format:"user2==%@",user1)letpredicateUser1From2=NSPredicate(format:"user1==%@",user2)letpredica