Firebase iOS SDK：如何在一个查询中获取多个数据

Question

I've seen how to retrieve multiple data in one query firebase so this might be a similar question, but I'm new to Firebase and I don't get it properly.

Here is my situation:

I have a Firebase database like this:

I want to retrieve users who participated in a particular event.
EDIT
i tried bellow,

Firebase* childrens = [server childByAppendingPath:@"Users"];
    Firebase* firebaseUser = [childrens childByAppendingPath:self.myuserid];
    Firebase* firebaseEvent = [firebaseUser childByAppendingPath:@"Events"];
    Firebase* fbuser= [firebaseEvent childByAppendingPath:@"Created"];
FQuery* query1 = [fbuser queryOrderedByChild:@"id"];
    handleFirebase = [query1 observeEventType:FEventTypeValue withBlock:^(FDataSnapshot *snapshot){
        NSEnumerator* childrens = snapshot.children;
        [childrens.allObjects enumerateObjectsUsingBlock:^(FDataSnapshot* rootSnap,NSUInteger rootIndex,BOOL* rootStop){
            NSDictionary* rootData = rootSnap.value;
            NSString* rootKey = rootSnap.key;
            NSLog(@"\nRootKey: %@\nRootData: %@",rootKey,rootData);
        }];

here is NSLog

2016-03-10 15:27:23.399 SquadApp[4425:110128] 
RootKey: olbuzevent1
RootData: {
    createdTime = "2016-03-08T11:53:33Z";
    name = "OLBUZ event 1";
    participents =     {
        "335e63c9-46c6-4ff8-99e7-1537d99731f7" =         {
            id = "335e63c9-46c6-4ff8-99e7-1537d99731f7";
            joinnedTime = 0;
        };
    };
}
2016-03-10 15:27:24.150 SquadApp[4425:110128] 
RootKey: olbuzevent2
RootData: {
    createdTime = "2016-03-08T12:23:28Z";
    name = "OLBUZ event 2";
    participents =     {
        "335e63c9-46c6-4ff8-99e7-1537d99731f7" =         {
            id = "335e63c9-46c6-4ff8-99e7-1537d99731f7";
            joinnedTime = 0;
        };
    };
}

Answer 1

In a NoSQL database you often have to model the data for the way you want to use it in your application. Your current structure is great for showing a list of events that the user organized/participated in. If that is one of your use-cases, that is great.

But if you also have a use-case to show all users that participated in an event, you'll likely have to add a data structure where you track that.

event_users
  eventid1
    uid1: 'participant'
    uid2: 'organizer'
    uid3: 'participant'

This process is known as denormalization and is covered in one of our (quite old) blog posts and in the documentation on structuring data . In that last page you should probably also read the recommendation on nesting .