decode Swift enum and Date for Codable properties

Codable+Extension.swift

import Foundation

protocol AssetTypeConvertible {
    // conformer just need to declare conformance to `AssetTypeConvertible` and will be auto inferred as generic `Value`
    // and Xcode auto completion just works
    // see AssetType below
    associatedtype Value = Self 
    static func convertToEnum(from rawValue: String) -> Value
}

extension KeyedDecodingContainerProtocol {
    func decodeEnumFromRawValue<T: AssetTypeConvertible>(_ rawValue: String) throws -> T {
        guard let result = T.convertToEnum(from: rawValue) as? T else {
            // this should never happen, since we inferred type
            fatalError("This should never happen, since we inferred type, but here is to not force cast")
        }

        return result
    }
}

struct Utilities {}
extension Utilities {
    static func decodeDate<T: CodingKey>(key: T, in container: KeyedDecodingContainer<T>, using dateFormatter: DateFormatter) throws -> Date {
        let _decoded = try container.decodeIfPresent(String.self, forKey: key) ?? ""
        return _decoded.isEmpty ? Date() : (dateFormatter.date(from: _decoded) ?? Date())
    }
}

// AssetTypeConvertible usage 

enum AssetType: String {
    case series
    case movie
    case sports
    case live
    case unknown = ""

    static func convert(from string: String) -> AssetType {
        return AssetType(rawValue: string) ?? .unknown
    }
}

// Conforms AssetType to AssetTypeConvertible protocol, so that it can be decoded in SearchItem decode
extension AssetType: AssetTypeConvertible {
    static func convertToEnum(from rawValue: String) -> AssetType {
        return .convert(from: rawValue)
    }
}

// Codable usage

struct SearchItem: Codable {

    // MARK: - Properties
    let assetType: AssetType
    let id: String
    let startDate: Date
    let endDate: Date

    // MARK: - Value Types
    private enum CodingKeys: String, CodingKey {
        case assetType = "AssetType"
        case id = "ID"
        case startDate, endDate
    }

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        assetType = try container.decodeEnumFromRawValue(try container.decode(String.self, forKey: .assetType))
        id = try container.decode(String.self, forKey: .id)
        startDate = try Utilities.decodeDate(key: .startDate, in: container, using: .searchDateFormatter)
        endDate = try Utilities.decodeDate(key: .endDate, in: container, using: .searchDateFormatter)
    }
}

// DateFormatter
extension DateFormatter {
    static var searchDateFormatter: DateFormatter {
        // 5/16/2019 11:55:00 AM
        let formatter = self.posixFormatter
        formatter.dateFormat = "MM/dd/yyyy h:mm:ss a"
        return formatter
    }

    static var posixFormatter: DateFormatter {
        // https://developer.apple.com/library/archive/qa/qa1480/_index.html
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        return formatter
    }
}