Swift struct with custom encoder and decoder cannot conform to 'Encodable' - swift

Question

[Edited to provide a minimal reproducible example ]
This is the complete struct without non relevant vars and functions
InstrumentSet.swift
import Foundation
struct InstrumentsSet: Identifiable, Codable {
private enum CodingKeys: String, CodingKey {
case name = "setName"
case tracks = "instrumentsConfig"
}
var id: String { name }
var name: String
var tracks: [Track]
}
Track.swift
import Foundation
extension InstrumentsSet {
struct Track: Identifiable, Encodable {
private enum TrackKeys: String, CodingKey {
case id = "trackId"
case effects
}
let id: String
var effects: [Effect]?
}
}
extension InstrumentsSet.Track: Decodable {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: TrackKeys.self)
id = try container.decode(String.self, forKey: .id)
effects = try container.decodeIfPresent([Effect].self, forKey: .effects)
}
}
Effect.swift
import Foundation
import AudioKit
import SoundpipeAudioKit
extension InstrumentsSet.Track {
enum Effect: Decodable {
private enum EffectKeys: String, CodingKey {
case effectType = "effectName"
case cutoffFrequency
case resonance
}
case lowPassFilter(LowPassFilterEffect)
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: EffectKeys.self)
let effectType = try container.decode(Effect.EffectType.self, forKey: .effectType)
switch effectType {
case .lowPassFilter:
let cutOffFrequency = try container.decode(ValueAndRange.self, forKey: .cutoffFrequency)
let resonance = try container.decode(ValueAndRange.self, forKey: .resonance)
self = .lowPassFilter(LowPassFilterEffect(cutOffFrequency: cutOffFrequency, resonance: resonance))
default:
fatalError("Not implemented!")
}
}
}
}
extension InstrumentsSet.Track.Effect {
enum EffectType: String, Decodable {
case lowPassFilter
}
}
extension InstrumentsSet.Track.Effect: Encodable {
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: EffectKeys.self)
//FIXME: This is the location of the error: Type 'ValueAndRange.Type' cannot conform to 'Encodable'
try container.encode(ValueAndRange.self, forKey: .cutoffFrequency)
}
}
The problem is ValueAndRange.self not not conforming to Encodable
I've followed multiple examples to get to this implementation:
import Foundation
import AudioKit
struct ValueAndRange: Encodable {
private enum ValueRangeKeys: String, CodingKey {
case value
case range
}
static var zero: ValueAndRange { .init(value: 0, range: [0, 0]) }
var value: AUValue
var range: [Double]
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: ValueRangeKeys.self)
try container.encode(value, forKey: .value)
try container.encode(range, forKey: .range)
}
}
extension ValueAndRange: Decodable {
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: ValueRangeKeys.self)
value = try container.decode(AUValue.self, forKey: .value)
range = try container.decode([Double].self, forKey: .range)
}
}
I cannot see why this struct should not conform to Encodable. Maybe any of you got betters eyes (and brains) then I got?

Answer 1

Your encode function is incorrectly trying to encode a type, ValueAndRange.self, rather than a value.
Looking at the init(from:) method I think your encode function should look something like this
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: EffectKeys.self)
switch self {
case .lowPassFilter(let effect):
try container.encode(effect.cutOffFrequency, forKey: .cutoffFrequency)
try container.encode(effect.resonance, forKey: .resonance)
}
}
I didn't include .effectType in this code since I am uncertain of its usage (isn't it always the same hard coded string?).