How to encode enum with Arrays of Custom Objects - swift

Question

Thanks for your help in advance! I am relatively new to SwiftUI and have been struggling with encoding an enum with Arrays of custom objects. Here is the code:
struct ChartData: Codable {
var data: DataType
...
private enum CodingKeys : String, CodingKey { case id, title, type, info, label_x, label_y, last_update, data }
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
...
try container.encode(self.data, forKey: .data)
}
}
enum DataType: Codable{
case plot([ChartPlotData])
case slice([ChartSliceData])
case number([ChartNumberData])
}
struct ChartPlotData: Codable {
var chart_id: String
var order_plot: Int
var label_plot: String?
var points_x: [String]
var points_y: [Double]
private enum CodingKeys : String, CodingKey { case chart_id, order_plot, label_plot, points_x, points_y }
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self.chart_id = try container.decode(String.self, forKey: .chart_id)
self.order_plot = try container.decode(Int.self, forKey: .order_plot)
self.label_plot = try? container.decode(String.self, forKey: .label_plot)
do{
self.points_x = try container.decode([String].self, forKey:.points_x)
}catch{
let xs = try container.decode([Double].self, forKey:.points_x)
self.points_x = xs.map { String($0) }
}
self.points_y = try container.decode([Double].self, forKey:.points_y)
}
}
struct ChartSliceData: Codable {
var chart_id: String
var order_slice: Int
var label_slice: String
var value_slice: Double
}
struct ChartNumberData: Codable {
var chart_id: String
var number: Double
var unit: String?
}
I am attempting to cache JSON in UserDefaults so as to avoid having to make extraneous API calls. Using JSONEncoder, I am left with the following JSON snippet (excerpted from a much longer string):
"data" : {
"plot" : {
"_0" : [
{
"label_plot" : "China",
"points_y" : [
0,
0,
0,
...
However, I am looking to get an encoding like this:
"data" : [
{
"label_plot" : "China",
"points_y" : [
0,
0,
0,
...
Any help would be greatly appreciated! Thanks so much!

Answer 1

This can be solved by adding an extra item in the CodingKeys enum for encoding and decoding the type used for the DataType enum and then using a switch to encode and decode the right type of array.
Here is the full ChartData struct although with some properties and code removed for brevity
struct ChartData: Codable {
var id: Int
var title: String
var data: DataType
enum CodingKeys: String, CodingKey {
case id, title, data, type
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(id, forKey: .id)
try container.encode(title, forKey: .title)
switch data {
case .number(let values):
try container.encode("number", forKey: .type)
try container.encode(values, forKey: .data)
case .plot(let values):
try container.encode("plot", forKey: .type)
try container.encode(values, forKey: .data)
case .slice(let values):
try container.encode("slice", forKey: .type)
try container.encode(values, forKey: .data)
}
}
init(from decoder: Decoder) throws {
var container = try decoder.container(keyedBy: CodingKeys.self)
id = try container.decode(Int.self, forKey: .id)
title = try container.decode(String.self, forKey: .title)
let type = try container.decode(String.self, forKey: .type)
switch type {
case "number":
let values = try container.decode([ChartNumberData].self, forKey: .data)
data = .number(values)
// case ...
default:
fatalError("Unsupported type for DataType: \(type)")
}
}
}