CODEWITHSUNDEEP
swiftfirebasefirebase-realtime-database
Catch
Catch

Reputation: 153

Not able to read `childChanged`

I want to listen for childChanged in my app. I have a firebaseStructure like this:

-counters
---currentLoggedInUsers : 4

I want to be able to listen to when currentLoggedInUsers changes.

My best effort is this: 

 ref?.child("counters").observe( .childChanged, with: { (snapshot) in
            let dict = snapshot.value as? [String : Int] ?? [:]
            print(snapshot) //Prints the correct value when updated

            self.currentLoggedInUsers = dict["currentLoggedInUsers"]! 
     })

the snapshot prints correctly when updated, but self. currentLoggedInUsers = dict["currentLoggedInUsers"]! gives error:

Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value

Upvotes: 0

Views: 47

Answers (1)

Jay
Jay

Reputation: 35648

This answer will depend on whether there are other child nodes stored within counters. So if it just this

counters
   currentLoggedInUsers: 2

then the following code should be used, keeping in mind that .value will cause the code in the closure to fire immediately.

let ref = self.ref.child("counters").child("currentLoggedInUsers")
ref.observe(.value, with: { snapshot in
    print(snapshot.key, snapshot.value)
})

as it is watching that specific child node for changes.

note self.ref points to my firebase as a class var

To expand a bit, suppose you have other child nodes within counters and you want to watch them for changes as well.

counters
   currentLoggedInUsers: 2
   totalUsers: 100
   usersFavFood: Tacos

and one way to handle that is

let ref = self.ref.child("counters")
ref.observe(.childChanged, with: { snapshot in
    let nodeKey = snapshot.key

    switch nodeKey {
    case "currentLoggedInUsers":
        let count = snapshot.value as? Int ?? 0
        print("logged in users changed to: \(count)")
    case "totalUsers":
        let totalCount = snapshot.value as? Int ?? 0
        print("total Users: \(totalCount)")
    case "usersFavFood":
        let food = snapshot.value as? String ?? "No food for you"
        print("favorite food changed to: \(food)")
    default:
        print("some node changed but it's not handled")
    }
})

Upvotes: 2

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