How to convert an array of custom classes to Data? - ios

Question

I want to convert an array of custom Note() classes to Data() to encrypt it later on and store it.
My class is
class Note: NSObject {
var text = "hi"
var date = Date()
}
The class above is an example. My class would be a bit more complex.
I've tried
let plistData = NSKeyedArchiver.archivedData(withRootObject: mergedNotes)
if let a: Array<Note> = NSKeyedUnarchiver.unarchiveObject(with: plistData) as? Array<Note> {
print(a)
}
The above code crashes with a signal sigabrt.
How does this work and is it possible without encoding an decoding the entire class?

Answer 1

First of all setup your Note class, must conform to the codable protocol:
class Note: Codable {
var text = "hi"
var date = Date()
init(t: String, d: Date) {
text = t
date = d
}
enum CodingKeys: String, CodingKey {
case text
case date
}
required init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
text = try container.decode(String.self, forKey: .text)
date = try container.decode(Date.self, forKey: .date)
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(text, forKey: .text)
try container.encode(date, forKey: .date)
}
}
Then you can create your array of notes:
let arrayOfNotes: [Note] = [Note(t: "someNote", d: Date())]
And just save it in user defaults:
do {
let encoded = try JSONEncoder().encode(arrayOfNotes)
UserDefaults.standard.set(encoded, forKey: "SavedNotes")
} catch let error {
// catch any error if present
print(error)
}
to retrive your saved data you can simply use an if let or a do-catch like above:
if let savedData = UserDefaults.standard.value(forKey: "SavedNotes") as? Data {
if let notes = try? JSONDecoder().decode(Note.self, from: savedData) {
// do whatever you need
}
}