firebase - get all chat rooms for a member - ios

Question

I'm integrating multi-room chat in my app and I'm stuck with getting a list of all chat room a specific user is member of.
The structure looks like this:
The rooms and members are created with childByAutoId like this:
FIRUser *user = [FIRAuth auth].currentUser;
mdata[#"uid"] = user.uid;
roomKey = [[_rootRef child:#"messages"] childByAutoId].key;
NSString *memberID = [[[_rootRef child:#"members"] child: roomKey ] child: user.uid ].key;
// set Meta data for member to be able to recognize later
[[[[_rootRef child:#"members"] child: roomKey ] child: memberID ] setValue:mdata];
Now I'm trying the get the list of rooms for a (hard coded) user like that:
-(void) getRoomKeys {
[[[[_rootRef child: #"members"] queryOrderedByChild:#"uid" ] queryEqualToValue:#"QLfRoGpoCjWpzira7fljBj8g3EJ3"]
observeEventType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot *snapshot) {
NSDictionary<NSString *, NSString *> *message = snapshot.value;
}];
}
This return 0 key/value pairs.
When I take out the query I get all room keys. When I change the structure to this
I will get all rooms for that user but with this structure I can't add other members to that room. So I need to dig one level deeper.
So how to set the query for nodes that have been created by childByAutoId?
Thanks for your help!

Answer 1

Try considering this data structure.
{
"rooms": {
"-KQgDxLIt88yPt6nacDu": { ... }
},
"members": {
"QLfRoGpoCjWpzira7fljBj8g3EJ3": { ... }
},
"member-rooms": {
"QLfRoGpoCjWpzira7fljBj8g3EJ3": {
"-KQgDxLIt88yPt6nacDu": true
}
}
}
You can retrieve the keys of the rooms a member is part of by observing member-rooms/{uid}:
[[_rootRef child: #"member-rooms/QLfRoGpoCjWpzira7fljBj8g3EJ3"] observeEventType:FIRDataEventTypeValue withBlock:^(FIRDataSnapshot *snapshot) {
NSLog("%#", snapshot.value); // the keys of the rooms of the member
}];