PickerInlineRow, PickerRow - Best Practices for populating options - ios

Question

Fairly new to iOS. I am using Firebase for the backend data, and I'm wondering about the recommended approach for populating option lists for things such as a PickerInlineRow. What I have typically done is the following;
Create variables to hold the data used in my form
Call Firebase to retrieve the data
Load the values from Firebase into my local variables
In the closure for the Firebase call, load the form
In the form, populate the values by using my variables
Update the variables using .onchange events
When the user saves, the variables are used to update the database. This all works, but the problem comes about when trying to populate dropdowns within the form. I know how to set options for the picker, but unclear as to how to structure the sequence so that the array I use for options is populated prior to use. If I set the options to an array, but the array hasn't finished populating, the picker has no values.
What's the recommended way to coordinate these events? I've pasted an example Eureka form below.
import UIKit
import Firebase
import GeoFire
import Eureka
class QuestDetailsViewController: FormViewController {
let ref: FIRDatabaseReference = FIRDatabase.database().reference()
var key = String()
var isNew = Bool()
var locationKeys = [String]()
var locationNames = [String]()
var locationKey: String?
var locationName: String?
var startDate: Date?
var endDate: Date?
override func viewDidLoad() {
super.viewDidLoad()
loadData()
}
func loadData(){
// load lookup values
if isNew == false {
ref.child("Quests").child(key).observeSingleEvent(of: .value, with: {(snapshot) in
if let item = snapshot.value as? [String:AnyObject]{
self.locationName = item["LocationName"] as? String
self.locationKey = item["LocationKey"] as? String
self.startDate = DateFromInterval(interval: (item["StartDate"] as? Double)!)
self.endDate = DateFromInterval(interval: (item["EndDate"] as? Double)!)
}
self.loadDropdowns()
} , withCancel: {error in
print("Error : \(error.localizedDescription)")
})
}
else {
self.loadDropdowns()
}
}
func loadDropdowns() {
ref.child("Places").queryOrdered(byChild: "PlaceName").observeSingleEvent(of: .value, with: {(snapshot) in
for item in (snapshot.children.allObjects as? [FIRDataSnapshot])! {
let thisPlace = item.value as! [String: AnyObject]
self.locationKeys.append(item.key)
self.locationNames.append(thisPlace["PlaceName"] as! String)
}
self.loadForm()
}, withCancel: {error in
})
}
func loadForm() {
form +++ PickerInlineRow<String>() {
$0.tag = "locationPicker"
$0.title = "Location"
$0.options = locationNames
$0.value = self.locationName
}.onChange({ (row) in
self.locationName = row.value
let itemIndex = self.locationNames.index(of: self.locationName!)
self.locationKey = self.locationKeys[itemIndex!]
})
<<< DateTimeRow() {
$0.tag = "startDate"
$0.title = "From"
$0.value = self.startDate
}.onChange({ (row) in
self.startDate = row.value
})
<<< DateTimeRow() {
$0.tag = "endDate"
$0.title = "To"
$0.value = self.endDate
}.onChange({ (row) in
self.endDate = row.value
})
+++ ButtonRow() {
$0.title = "Challenges"
$0.presentationMode = PresentationMode.segueName(segueName: "segueChallenges", onDismiss: nil)
}
+++ ButtonRow() {
$0.title = "Save Changes"
}.onCellSelection({ (cell, row) in
self.saveChanges()
})
}
func saveChanges() {
let childUpdates = ["LocationKey": locationKey!, "LocationName": locationName!, "StartDate": IntervalFromDate(date: startDate!), "EndDate": IntervalFromDate(date: endDate!)] as [String : Any]
if isNew == true {
key = ref.child("Quests").childByAutoId().key
}
ref.child("Quests").child(key).updateChildValues(childUpdates, withCompletionBlock: {(error, ref) in
self.navigationController?.popViewController(animated: true)
})
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "segueChallenges" {
let vc = segue.destination as? ChallengesTableViewController
vc?.questKey = key
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

You want to load the form without any values, then when the values come back from firebase, you can reload the rows using row tags
//Completion handler of Firebase {
if let row = self.form.rowBy(tag: "rowTag") as? PickerInlineRow<RowType> {
row.reload()
}
}