JSON return nil check? - json

Question

struct AltWX: Decodable {
var raw: String
}
typealias AltMetarDecode = [String: AltWX]
do
{
let aero = try decoder.decode(AltMetarDecode.self, from: data)
DispatchQueue.main.async {
if self.DownloadOrderCode == 3
{
if let Ab = aero[ICAO1]
{
self.Alternate1Metar.text = Ab.raw
UserDefaults.standard.set(Ab.raw, forKey: "MetarCodeAlt1")
}
}
...
The above code accesses a Json like this:
"xxxx": { "raw": "Test"
so Ab.raw would print Test
How can I add an error check to see if ICAO1 exists and also if Ab.raw exists, and if any values are nil return something? I read the usual catch responses to Json but not sure how to format it for this case specifically especially that i have a lot of order codes and each has to be checked separately.

Answer 1

This checks if ICAO1 exists and raw is empty
if let raw = aero["ICAO1"]?.raw, raw.isEmpty {
}
Please name variables lowercased according to the naming convention.

Answer 2

I think you want a do try catch block for this.
enum ContentError: Error {
case missingICAO1
case missingRaw
case orderCodeError
}
// not sure of the return types from the decode block ???
func setValues(values: AltMetarDecode) throws {
guard self.DownloadOrderCode == 3 else { throw ContentError.orderCodeError }
guard let Ab = values[ICA01] else { throw ContentError.missingICA01 }
guard Ab.raw != nil else { throw ContentError.missingRaw }
self.Alternate1Metar.test = Ab.raw
UserDefaults.standard.set(Ab.raw, forKey: "MetarCodeAlt1")
}
do {
let aero = try decoder.decode(AltMetaDecode.self, from data)
try DispatchQueue.main.async {
setValues(values: aero)
}
} catch {
print(error)
}
Setting up a function to throw errors may not be the most code efficient way, but to me it makes the code clear and readable.