Using Firebase observeSingleEventOfType synchronously

Question

I am trying to use a semaphore to force synchronisation of a Firebase data query so that I can check for an existing item already in the database.

This is the code

Answer 1

You might be intersted in using a completion handler.

func findUniqueId(completion:(uniqueId:String)->()) {
    self.firDB.child("sessions").observeSingleEventOfType(.Value, withBlock: { snapshot in
        var sID = self.genCode()
        while snapshot.hasChild(sID) {
            sID = self.genCode()
        }
        completion(uniqueId:sID)
    })
}

Then you will achieve what you are expecting with

findUniqueId(){ (uniqueId:String) in
    // this will only be called when findUniqueId trigger completion(sID)...
    print(uniqueId)
    // proceed with you logic...
}