Decoding an enum containing bools - ios

Question

I have this JSON file.
[
{
"name": "January",
"holidays": [
{
"name": "New Year's Day",
"date": "2019-01-01T00:00:00-0500",
"type": {
"isNationalHoliday": true,
"isRegionalHoliday": true,
"isPublicHoliday": true,
"isGovernmentHoliday": true
}
},
{
"name": "Martin Luther King Day",
"date": "2019-01-21T00:00:00-0500",
"type": {
"isNationalHoliday": true,
"isRegionalHoliday": true,
"isPublicHoliday": true,
"isGovernmentHoliday": true
}
}
]
},
{
"name": "February",
"holidays": [
{
"name": "Presidents' Day",
"date": "2019-02-18T00:00:00-0500",
"type": {
"isNationalHoliday": false,
"isRegionalHoliday": true,
"isPublicHoliday": false,
"isGovernmentHoliday": false
}
}
]
},
{
"name": "March",
"holidays": null
}
]
I created a Month struct to decode the dictionaries in the JSON.
public struct Month {
public let name: String
public let holidays: [Holiday]?
}
extension Month: Decodable { }
And an Year struct to contain them all.
public struct Year {
public let months: [Month]
}
extension Year: Decodable {
public init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
let values = try container.decode([Month].self)
months = values
}
}
My Holiday struct is a little more complex due to having an enum called HolidayType where I want to decode the values under the type field in the JSON.
public struct Holiday {
public let name: String
public let date: Date
public let type: HolidayType
}
extension Holiday: Decodable { }
public enum HolidayType {
case isNationalHoliday
case isRegionalHoliday
case isPublicHoliday
case isGovernmentHoliday
enum CodingKeys: String, CodingKey {
case isNationalHoliday
case isRegionalHoliday
case isPublicHoliday
case isGovernmentHoliday
}
}
extension HolidayType: Decodable {
public init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self = try container.decode(HolidayType.self, forKey: .isNationalHoliday)
self = try container.decode(HolidayType.self, forKey: .isRegionalHoliday)
self = try container.decode(HolidayType.self, forKey: .isPublicHoliday)
self = try container.decode(HolidayType.self, forKey: .isGovernmentHoliday)
}
}
This is where I'm loading the file and decoding.
if let url = Bundle.main.url(forResource: "holidays", withExtension: "json") {
do {
let data = try Data(contentsOf: url)
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
let year = try decoder.decode(Year.self, from: data)
print(year.months)
} catch let error {
print("Error occurred decoding JSON: \(error)")
}
} else {
print("Error occurred loading file")
}
But it fails with the following error.
typeMismatch(Swift.Dictionary,
Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index
0", intValue: 0), CodingKeys(stringValue: "holidays", intValue: nil),
_JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "type", intValue: nil), CodingKeys(stringValue: "isNationalHoliday",
intValue: nil)], debugDescription: "Expected to decode
Dictionary but found a number instead.", underlyingError:
nil))
I can't figure out how to fix this. I also uploaded a demo project here.

Answer 1

You cannot use an enum to represent multiple booleans. If you want to keep your types without change, I would recommend using an OptionSet with custom decoding:
struct Year: Decodable {
let months: [Month]
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
months = try container.decode([Month].self)
}
}
struct Month: Decodable {
let name: String
let holidays: [Holiday]?
}
struct Holiday: Decodable {
let name: String
let date: Date
let type: HolidayType
}
struct HolidayType: OptionSet, Decodable {
let rawValue: Int
static let national = HolidayType(rawValue: 1 << 0)
static let regional = HolidayType(rawValue: 1 << 1)
static let `public` = HolidayType(rawValue: 1 << 2)
static let government = HolidayType(rawValue: 1 << 3)
init(rawValue: Int) {
self.rawValue = rawValue
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
self = try CodingKeys.allCases
.filter { try container.decode(Bool.self, forKey: $0) }
.map { $0.type }
.reduce([] as HolidayType) { $0.union($1) }
}
private enum CodingKeys: String, CodingKey, CaseIterable {
case isNationalHoliday
case isRegionalHoliday
case isPublicHoliday
case isGovernmentHoliday
var type: HolidayType {
switch self {
case .isNationalHoliday:
return .national
case .isRegionalHoliday:
return .regional
case .isPublicHoliday:
return .public
case .isGovernmentHoliday:
return .government
}
}
}
}
or, instead of custom parsing, you can translate your types using a computed variable:
struct Holiday: Decodable {
let name: String
let date: Date
private let type: HolidayTypeHolder
var types: [HolidayType] {
return type.types
}
}
enum HolidayType: String {
case national, regional, `public`, `government`
}
private struct HolidayTypeHolder: Decodable {
let isNationalHoliday, isRegionalHoliday, isPublicHoliday, isGovernmentHoliday: Bool
var types: [HolidayType] {
var types: [HolidayType] = []
if isNationalHoliday {
types.append(.national)
}
if isRegionalHoliday {
types.append(.regional)
}
if isPublicHoliday {
types.append(.public)
}
if isGovernmentHoliday {
types.append(.government)
}
return types
}
}

Answer 2

"isNationalHoliday", intValue: nil)], debugDescription: "Expected to decode Dictionary but found a number instead.", underlyingError: nil))
isNationalHoliday is a bool value not an enum type , so on for isRegionalHoliday, isPublicHoliday, isGovernmentHoliday
You need
// MARK: - Element
struct Root: Codable {
let name: String
let holidays: [Holiday]?
}
// MARK: - Holiday
struct Holiday: Codable {
let name: String
let date: Date
let type: TypeClass
}
// MARK: - TypeClass
struct TypeClass: Codable {
let isNationalHoliday, isRegionalHoliday, isPublicHoliday, isGovernmentHoliday: Bool
}
let year = try decoder.decode([Root].self, from: data)