Update firebase database with time-based key on iOS - ios

Question

I'm using Firebase and iOS to keep a time series of an integer value over the last 24 hours. I have tried using both the .updateChildValues() and .setValue() from the docs, but haven't yet figured out how to keep firebase from overwriting every child value, not just the child value with the same key.
func writeStepsPost(withUserID userID: String, steps: NSNumber) {
let timeStamp = NSDate().timeIntervalSince1970 as NSNumber
let post_user: NSString = userID as NSString
let value: NSNumber = steps
let post = ["uid": post_user,
"steps": value,
"lastUpdate":timeStamp]
let childUpdates = ["/posts-steps-user/\(userID)/": post]
ref.updateChildValues(childUpdates)
let currentHour = Calendar.current.component(.hour, from: Date())
let hourlyPost = ["steps":value]
let dailyUpdates = ["/posts-steps-user/\(userID)/pastDay/\(currentHour):00/": hourlyPost]
print("posting hourly steps update")
ref.updateChildValues(dailyUpdates)
When the time changes from 10 to 11, the node for '10:00':123 is replaced by '11:00':243, when I need to add a node for 11 while leaving 10 in place until the next day. I suspect that since the function is pushing two updates, the first update replaces the existing node.
Any ideas?

Answer 1

Given a single key path like /posts-steps-user/\(userID)/, updateChildValues only updates data at the first child level, and any data passed in beyond the first child level is a treated as a setValue operation. Multi-path behavior allows longer paths to be used without overwriting data. It is documented very well in this Firebase Documentation.
I've tested with the following adjustment to your code where I define multiple paths for your first updateChildValues so it won't overwrite your pastDay and it is working properly.
let childUpdatePath = "/posts-steps-user/\(userID)/"
ref.updateChildValues([
"\(childUpdatePath)/uid": post_user,
"\(childUpdatePath)/steps": value,
"\(childUpdatePath)/lastUpdate": timeStamp
])
let currentHour = Calendar.current.component(.hour, from: Date())
let hourlyPost = ["steps":value]
let dailyUpdates = ["/posts-steps-user/\(userID)/pastDay/\(currentHour):00/": hourlyPost]
ref.updateChildValues(dailyUpdates)