PersistentReusableContainer.swift

struct EventItem: ContainerItem, Codable {
    let date: Date
    let title: String
    let description: String
}

struct NoteItem: ContainerItem, Codable {
    let text: String
}

enum CalendarKeys: String {
    case homeEvents, workEvents, notes
}

extension Container where Key == CalendarKeys {
    convenience init(contentsOfURL url: URL) throws {
        let data = try Data(contentsOf: url)
        let contents = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as! [Key.RawValue: [Data]]
        let converted = contents.compactMap({ (keyValuePair) -> (Key, [ContainerItem])? in
            guard let key = Key(rawValue: keyValuePair.key) else { return nil }
            switch key {
            case .homeEvents, .workEvents:
                return (key, keyValuePair.value.compactMap({ EventItem(jsonData: $0) }))
            case .notes:
                return (key, keyValuePair.value.compactMap({ NoteItem(jsonData: $0) }))
            }
        })
        self.init(content: Dictionary(uniqueKeysWithValues: converted))
    }
}

extension Container where Key.RawValue == String {
    func write(to url: URL) throws {
        let converted = storage.map { (keyValuePair) -> (String, [Data]) in
            return (keyValuePair.key.rawValue, keyValuePair.value.map({ $0.jsonDataRepresentation }))
        }
        let data = try NSKeyedArchiver.archivedData(withRootObject: Dictionary(uniqueKeysWithValues: converted), requiringSecureCoding: false)
        try data.write(to: url, options: .atomicWrite)
    }
}