JSONDecoder but sometimes the key is missing, how to replace data - Swift - arrays

Question

I'm trying to decode a JSON result in Swift but sometimes one of the keys is missing in the JSON which is causing my attempt at decoding to crash. I cannot figure out a way to replace a missing key with a value to prevent it from crashing and to keep my data structured and in line with other arrays and their positions.
It works perfectly unless there is a missing key from the API, in which case I'm getting a crash.
Here is my code:
import Foundation
#if canImport(FoundationNetworking)
import FoundationNetworking
#endif
struct PortHW: Codable {
let EventType: String
let DateTime: String
let Height: Double
}
func getPortHW(portID: String) -> (eventArray: [String], timeArray: [String], heightArray: [Double]) {
var json: Data? = nil
let semaphore = DispatchSemaphore (value: 0)
var request = URLRequest(url: URL(string: "https://admiraltyapi.azure-api.net/uktidalapi/api/V1/Stations/\(portID)/TidalEvents?duration=7")!,timeoutInterval: Double.infinity)
request.addValue("HIDDEN", forHTTPHeaderField: "Ocp-Apim-Subscription-Key")
request.httpMethod = "GET"
let task = URLSession.shared.dataTask(with: request) { data, response, error in
guard let data = data else {
print(String(describing: error))
semaphore.signal()
return
}
json = data
semaphore.signal()
}
task.resume()
semaphore.wait()
let decoder = JSONDecoder()
let tideResult = try? decoder.decode([PortHW].self, from: json!)
var eventArray: [String] = []
var timeArray: [String] = []
var heightArray: [Double] = []
for item in tideResult! {
eventArray.append(item.EventType)
timeArray.append(item.DateTime)
heightArray.append(item.Height)
}
return (eventArray, timeArray, heightArray)
}
The JSON I'm getting my data from looks like this most of the time:
[
{
"EventType": "HighWater",
"DateTime": "2022-03-15T01:29:00",
"IsApproximateTime": false,
"Height": 4.2845989326570688,
"IsApproximateHeight": false,
"Filtered": false,
"Date": "2022-03-15T00:00:00"
},
But sometimes the key Height is missing, not empty, but missing... I've struggled with finding a way to replace the missing key with a value of 0.0 when it's not there.. I'd really appreciate some guidance.
Thank you.

Answer 1

whichever is missing, you can make it optional
like this:
struct PortHW: Codable {
let EventType: String
let DateTime: String
let Height: Double?
}
extension PortHW {
func getHeight() -> Double {
if let height = self.Height {
return height
}
return 0.0
}
}
or you can just add defaultValue ==> 0.0
for item in tideResult! {
eventArray.append(item.EventType)
timeArray.append(item.DateTime)
heightArray.append(item.Height ?? 0.0)
}