NSDictionary firstIndex identification Swift 5 - json

Question

I'm working on an app where I need to store a Country and City in a Firebase database.
Besides storing, I also need to retrieve that info and present to the user in a pickerView. Given that, I need to read the Country and City from the Database, check what is their index and set it in pickerView.
Countries and Cities are store in JSON
{
"Country": [
{
"name": "UK",
"cities": [
{
"name": "London"
},
{
"name": "Manchester"
},
{
"name": "Bristol"
}
]
},
{
"name": "USA",
"cities": [
{
"name": "New York"
},
{
"name": "Chicago"
}
]
},
{
"name": "China",
"cities": [
{
"name": "Beijing"
},
{
"name": "Shanghai"
},
{
"name": "Shenzhen"
},
{
"name": "Hong Kong"
}
]
}
]
}
My code to read JSON is
// Declared in Class
var countryList = [NSDictionary]()
var selectedRow = [NSDictionary]()
var selectedCity = ""
var selectedCountry = ""
func readJson() {
if let path = Bundle.main.path(forResource: "Countries", ofType: "json") {
do {
let data = try Data(contentsOf: URL(fileURLWithPath: path), options: .mappedIfSafe)
let jsonResult = try JSONSerialization.jsonObject(with: data, options: .mutableLeaves)
if let jsonResult = jsonResult as? Dictionary<String, AnyObject>, let country = jsonResult["Country"] as? [NSDictionary] {
//handles the array of countries on your json file.
self.countryList = country
self.selectedRow = self.countryList.first?.object(forKey: "cities") as! [NSDictionary]
}
} catch {
print("error loading countries")
// handle error
}
}
}
The code above allows me to feed a UIPickerView with 2 sessions and the Country and the list of cities within that Country. From there, I can also identify which Country and City were selected.
AS part of my code I have a func that would allow me to identify what is indexes of the saved Country(countryIndex) and City(cityIndex) in UIPickerView so that I can set it and that's where my issues start
func indexOf(city: String, inCountry country: String, in countries: [Country]) -> (countryIndex: Int, cityIndex: Int)? {
// countries is an array of [Country]
// var countries = [Country]()
guard let countryIndex = countries.firstIndex(where: {$0.name == country}), let cityIndex = countries[countryIndex].cities.firstIndex(where: {$0.name == city}) else {return nil}
//let cityIndex = 0
return (countryIndex, cityIndex)
} // courtesy of #flanker
This func was working perfectly fine when my Countries and Cities were stored to a [Country] but is not working with NSDictionary coming from JSON.
I have tried to
1) Change [Country] by [NSDictionary], "countries" by "countryList" and "name" by "Country"
Here I receive and error "NSDictionary has no member Country"
I also tried to leave just $0 == Country which hasn't worked as well.
2) Tried also "countryList.firstIndex(of: "USA")" but got the error below
Cannot convert value of type 'String' to expected argument type 'NSDictionary'
Anyone would be able to assist? How can I make the func indexOf work again?
Thanks
Updated according to #vadian's suggestion
My updated code is
import UIKit
class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
#IBOutlet weak var pickerView: UIPickerView!
#IBOutlet weak var countryLbl: UILabel!
var familyNames: [String] = []
var fontName = "Arial"
let fontCount = 0
var countryList = [Country]()
var selectedRow = [City]()
var selectedCity : City?
var selectedCountry : Country?
struct Root : Decodable {
let country : [Country] // better plural let countries
private enum CodingKeys : String, CodingKey { case country = "Country" }
}
struct Country : Decodable {
var name : String
var cities : [City]
}
struct City : Decodable {
var name : String
}
override func viewDidLoad() {
super.viewDidLoad()
pickerView.delegate = self
pickerView.dataSource = self
fontName = "HelveticaNeue"
}
func indexOf(city: String, inCountry country: String, in countries: [Country]) -> (countryIndex: Int, cityIndex: Int)? {
guard let countryIndex = countries.firstIndex(where: {$0.name == country}), let cityIndex = countries[countryIndex].cities.firstIndex(where: {$0.name == city}) else {return nil}
return (countryIndex, cityIndex)
}
func pickerView(_ pickerView: UIPickerView, widthForComponent component: Int) -> CGFloat {
if component == 0 {
return 80
} else {
return 300
}
}
func numberOfComponents(in pickerView: UIPickerView) -> Int {
return 2
}
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
if component == 0 {
return countryList.count
} else {
return selectedRow.count
}
}
func pickerView(_ pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusing view: UIView?) -> UIView {
var rowTitle = ""
let pickerLabel = UILabel()
pickerLabel.textColor = UIColor.blue
switch component {
case 0:
rowTitle = countryList[row].name
case 1:
rowTitle = selectedRow[row].name
default:
break
}
pickerLabel.text = rowTitle
pickerLabel.font = UIFont(name: fontName, size: 20.0)
pickerLabel.textAlignment = .center
return pickerLabel
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
pickerView.reloadAllComponents()
if component == 0 {
self.selectedCountry = self.countryList[row]
self.selectedRow = self.countryList[row].cities
pickerView.reloadComponent(1)
self.pickerView.selectRow(0, inComponent: 1, animated: true)
self.selectedCity = self.selectedRow[0]
} else {
self.selectedCity = self.selectedRow[row]
}
if let indexes = indexOf(city: self.selectedCity!.name, inCountry: self.selectedCountry!.name, in: countryList) {
//do something with indexes.countryIndex and indexes.cityIndex
print("This is the result \(indexes.cityIndex) and \(indexes.countryIndex)")
}
countryLbl.text = "The right answer is: \(self.selectedCountry?.name) and the city is \(self.selectedCity?.name)"
}
func readJson() {
let url = Bundle.main.url(forResource: "Countries", withExtension: "json")!
do {
let data = try Data(contentsOf: url)
let jsonResult = try JSONDecoder().decode(Root.self, from: data)
//handles the array of countries on your json file.
self.countryList = jsonResult.country
self.selectedRow = self.countryList.first!.cities
} catch {
print("error loading countries", error)
}
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
readJson()
}
}

Answer 1

You have to decode the JSON in the bundle also into custom structs
struct Root : Decodable {
let country : [Country] // better plural let countries
private enum CodingKeys : String, CodingKey { case country = "Country" }
}
struct Country : Decodable {
let name : String
let cities : [City]
}
struct City : Decodable {
let name : String
}
var countryList = [Country]()
var selectedRow : [City]()
var selectedCity : City?
var selectedCountry : Country?
func readJson() {
let url = Bundle.main.url(forResource: "Countries", withExtension: "json")!
do {
let data = try Data(contentsOf: url)
let jsonResult = try JSONDecoder().decode(Root.self, from: data)
//handles the array of countries on your json file.
self.countryList = jsonResult.country
self.selectedRow = self.countryList.first!.cities
} catch {
print("error loading countries", error)
}
}
Then your method indexOf(city:inCountry:in:) works
As the file is in the application bundle consider to omit the root dictionary "Country" and decode [Country].self.
The usual side notes:
Do not use NS... collection types in Swift. You throw away the type information. Use native types.
.mutableContainers and .mutableLeaves are pointless in Swift. Apart from that ironically you assign the value to an immutable constant anyway.
A JSON dictionary in Swift 3+ is always value type [String:Any] not reference type[String:AnyObject].