Swift4 - JSON Decodable issue with array (Cannot subscript a value)

Question

I'm parsing weather JSON using Swift 4 Decodable, and i have an issue with array data. I'm think i may be a bit wrong with model (because there are bunch of decodable structs), please help.

JSON Data from the weather API:

{"coord":{"lon":-43.21,"lat":-22.9},"weather":[{"id":800,"main":"Clear","description":"clear sky","icon":"01d"}],
"base":"stations","main":{"temp":299.37,"pressure":1008,"humidity":51,"temp_min":296.15,"temp_max":302.15},
"visibility":10000,"wind":{"speed":4.1,"deg":320},"clouds":{"all":0},
"dt":1510909200,"sys":{"type":1,"id":4565,"message":0.0023,"country":"BR","sunrise":1510905615,
"sunset":1510953350},"id":3451190,"name":"Rio de Janeiro","cod":200}

Model:

struct WeatherData:Decodable {
let coord:CoordDict?
let weather:[WeatherArr]?
let base: String?
let main:MainDict?
let visibility:Int?
let wind:WindDict?
let clouds:CloudsDict?
let dt:Int?
let sys:SysDict?
let id:Int?
let name:String?
let cod:Int?}

struct CoordDict:Decodable {
let lon: Double?
let lat: Double?}

struct WeatherArr:Decodable {
let id: Int?
let main:String?
let description:String?
let icon: String?}

struct MainDict:Decodable {
let temp:Double?
let pressure:Double?
let humidity:Int?
let temp_min:Double?
let temp_max:Double?
let sea_level:Double?
let grnd_level:Double?}

struct WindDict:Decodable {
let speed:Double?
let deg:Double?}

struct CloudsDict:Decodable {
let all: Int?}

struct SysDict:Decodable {
let type:Int?
let id:Int?
let message:Double?
let country:String?
let sunrise:Int?
let sunset:Int?}

Parsing JSON data using JSONDecoder:

    let jsonUrlString = ("https://api.openweathermap.org/data/2.5/weather?lat=\(lat!)&lon=\(lon!)&APPID=\(apikey)")

    guard let url = URL(string: jsonUrlString) else { return }

    URLSession.shared.dataTask(with: url) { (data, response, err) in

        //check err
        if err != nil {
            print("Error:\(String(describing: err))")
        }

        guard let data = data else { return }
        //do stuff

        do {

            let weatherData = try JSONDecoder().decode(WeatherData.self, from: data)

            print(weatherData.name, weatherData.weather)

   //Here i can't parse the weather Array, and get xcode error

     if let wArr = weatherData.weather! as? Array<AnyObject> {
                if let weatherIcon = wArr["icon"] {
                  icon = weatherIcon
                    }
                }
        } catch let jsonErr {
            print("Error:\(jsonErr)")
        }

        }.resume()//URLSession

ERROR msg: Cannot subscript a value of type 'Array' with an index of type 'String'.

How can i fix this? How can i parse weather array elements?

The error is pretty clear. An array is index based, it has to be subscripted with an Int. Rather than a dictionary which is key based, it has to be subscripted with a String. By the way: openweathermap sends very reliable data. It's nonsensical to declare any property carelessly as optional. — vadian
– vadian, Commented Nov 17, 2017 at 10:40
It's clear. But in this case i have an issue with '[weatherArr]' type, in main weather struct. Cast from '[weatherArr]' to any unrelated type Array or Dictionary always fails. I have no idea how to make it properly in this case. — Rurom
– Rurom, Commented Nov 17, 2017 at 10:58
[weatherArr] is [weatherArr] (by the way structs are supposed to start with a capital letter), there's no need to cast a concrete type to a more unspecified one. Remove the type cast and get the first element with [0] or with first and optional binding. — vadian
– vadian, Commented Nov 17, 2017 at 11:01
Vadian, thank you for your patience. Well... the [weatherArr] contain only 1 element, it's a struct, it's not a surprise. Please give me advice, how can i get/parse the data from this struct further?? Please check the screenshot imgur.com/a/MpnIM — Rurom
– Rurom, Commented Nov 17, 2017 at 11:48

vadian · Accepted Answer · 2017-11-17 12:15:23Z

2

Declare weather in the WeatherData struct as non-optional. There is always a weather

let weather : [WeatherArr]

Get the first item if the array and the icon

if let currentWeather = weatherData.weather.first {
   if let weatherIcon = currentWeather.icon  {
      print(weatherIcon)
   }
}

edited Nov 17, 2017 at 12:15

answered Nov 17, 2017 at 11:54

vadian

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3 Comments

vadian Over a year ago

I mean to declare weather in the WeatherData struct as non-optional (remove the question mark)

vadian Over a year ago

Oh, silly me, we are dealing with structs. I updated the answer.

Rurom Over a year ago

Well Done! Thank you very much!

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