encodeWithCoder unrecognized selector sent to instance - ios

Question

I am getting this exception but I can't figure out where I'm going wrong. I am writing an extension to attempt to save this struct from the NewsAPISwiftLibrary to NSUserDefaults: NewsAPISource
This is the code to my extension:
extension NewsAPISource {
init?(data: NSData) {
if let coding = NSKeyedUnarchiver.unarchiveObject(with: data as Data) as? Encoding {
id = coding.id
name = coding.name
sourceDescription = coding.sourceDescription
url = coding.url
category = coding.category
language = coding.language
country = coding.country
sortBysAvailable = coding.sortBysAvailable as [SortBy]
} else {
return nil
}
}
func encode() -> NSData {
return NSKeyedArchiver.archivedData(withRootObject: Encoding(self)) as NSData
}
private class Encoding: NSObject, NSCoding {
let id: SourceId?
let name: String?
let sourceDescription: String?
let url: String?
let category: NewsAPISwift.Category?
let language: Language?
let country: Country?
let sortBysAvailable: [SortBy]
init(_ source: NewsAPISource) {
id = source.id
name = source.name
sourceDescription = source.sourceDescription
url = source.url
category = source.category
language = source.language
country = source.country
sortBysAvailable = source.sortBysAvailable
}
required init?(coder aDecoder: NSCoder) {
id = aDecoder.decodeObject(forKey: "id") as? SourceId
name = aDecoder.decodeObject(forKey: "name") as? String
sourceDescription = aDecoder.decodeObject(forKey:"sourceDescription") as? String
url = aDecoder.decodeObject(forKey: "url") as? String
category = aDecoder.decodeObject(forKey: "category") as? NewsAPISwift.Category
language = aDecoder.decodeObject(forKey: "language") as? Language
country = aDecoder.decodeObject(forKey: "country") as? Country
if let sorts = aDecoder.decodeObject(forKey: "sortBysAvailable") as? [SortBy] {
self.sortBysAvailable = sorts
} else {
return nil
}
}
func encode(with aCoder: NSCoder) {
aCoder.encode(id, forKey: "id")
aCoder.encode(name, forKey: "name")
aCoder.encode(sourceDescription, forKey: "sourceDescription")
aCoder.encode(url, forKey: "url")
aCoder.encode(category, forKey: "category")
aCoder.encode(language, forKey: "language")
aCoder.encode(country, forKey: "country")
aCoder.encode(sortBysAvailable, forKey: "sortBysAvailable")
}
}
}
I create a new struct like this:
let emptySource = NewsAPISource(id: "nil", name: "nil", sourceDescription: "nil", url: "nil", category: .business, language: .english, country: .unitedStates, sortBysAvailable: [.top])
and attempt to encode it like this:
emptySourceArray.encode()
This is the line that causes the exception. Any ideas on what I'm doing incorrectly?
The full error is:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[_SwiftValue encodeWithCoder:]: unrecognized selector sent to instance 0x60800005f4d0'