NSCoding support for Swift Structs. Save and load your Swift Structs from disk!

StructCoding.swift

import UIKit

public struct PersonItem
{
    var title: String
    
    init(title: String) {
        self.title = title
    }
}

extension PersonItem
{
    class Adapter: NSObject, NSCoding
    {
        let personItem: PersonItem
        
        init(personItem: PersonItem)
        {
            self.personItem = personItem
            super.init()
        }
        
        // PersonItem.Adapter supports encoding, decoding
        
        required init?(coder aDecoder: NSCoder)
        {
            guard let title = aDecoder.decodeObject(forKey: "title") as? String else { return nil }

            personItem = PersonItem(title: title)
            
            super.init()
        }
        
        public func encode(with aCoder: NSCoder)
        {
            aCoder.encode(personItem.title, forKey: "title")
        }
    }
    
    // class methods
    
    static func save(personItemsArray: [PersonItem], to url: URL) -> Bool
    {
        let personObjects = personItemsArray.map{Adapter(personItem: $0)}
        return NSKeyedArchiver.archiveRootObject(personObjects, toFile: url.path)
    }
    
    static func load(from url: URL) -> [PersonItem]?
    {
        let result = NSKeyedUnarchiver.unarchiveObject(withFile: url.path)
        return (result as? [Adapter])?.map{$0.personItem}
    }
}

let person1 = PersonItem(title: "Bob")
let person2 = PersonItem(title: "Nils")

let persons = [person1, person2]

let documentsUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let personCacheUrl = documentsUrl.appendingPathComponent("persons.archive")

let success = PersonItem.save(personItemsArray: persons, to: personCacheUrl)

let personsFromDisk = PersonItem.load(from: personCacheUrl)