Swift - How to Encode & Decode Array of Struct Objects

a) you should also post the code snippets and messages how you tried to save & load stocksArray and the exact error message

b) you can not save an single item in `func saveStocksArray() -> Bool` and retrieve it as an array in `func loadStocksArray() -> [Stock]?`

have you edited the code in the post ?

In fact,

1. var stock: Stock? init(stock: Stock) {
2. self.stock = stock super.init() }

seems erroneous, lacking a ; : self.stock = stock; super.init()

You need to define encoding in the struct itself as well, with your code :

func encode(with aCoder: NSCoder) {

aCoder.encode(companyName, forKey: "companyName")

aCoder.encode(symbol, forKey: "symbol")

aCoder.encode(price, forKey: "price")

}

}

Maybe the simplest would be to replace directly struct by a class

First of all, your `saveStocksArray` needs to pass an `NSArray` containing `StockClass` to `NSKeyedArchiver.archiveRootObject(_:toFile:)`, not a single object of `StockClass`. You may need to take an Array as a method parameter.

So, any of your 3 methods in `Stock` does not depend on a single instance, which means they should be type methods rather than instance methods.

Second, you get an `NSArray` containing `StockClass` from `NSKeyedUnarchiver.unarchiveObject(withFile:)` in your `loadStocksArray`, you need to explicitly convert it to an Array of `Stock`, which `as?`-casting won't do.

Third, I do not prefer using `NSString` just for using `appendingPathComponent(_:)`. (Sorry, this is just a problem of preference, not a critical issue.)

All three things fixed as well as fixing missing line breaks (you'd better fix your post), you can write something like this:

import UIKit
import Foundation

enum Path: String { case Stock = "Stock" }

struct Stock {
    var companyName: String?
    var symbol: String?
    var price: Double?
}
extension Stock {
    class StockClass: NSObject, NSCoding {
        var stock: Stock
        init(stock: Stock) {
            self.stock = stock
            super.init()
        }
       
        required init?(coder aDecoder: NSCoder) {
            guard let companyName = aDecoder.decodeObject(forKey: "companyName") as? String else { return nil }
            guard let symbol = aDecoder.decodeObject(forKey: "symbol") as? String else { return nil }
            guard let price = aDecoder.decodeObject(forKey: "price") as? Double else { return nil }
            
            stock = Stock(companyName: companyName, symbol: symbol, price: price)
            super.init()
        }
       
        func encode(with aCoder: NSCoder) {
            aCoder.encode(stock.companyName, forKey: "companyName")
            aCoder.encode(stock.symbol, forKey: "symbol")
            aCoder.encode(stock.price, forKey: "price")
        }
    }
   
    static func documentsDirectoryURL() -> URL {
        let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return urls[0]
    }
   
    static func saveStocksArray(stocksArray: [Stock]) -> Bool {
        let stockObjects = stocksArray.map{StockClass(stock: $0)}
        let file = documentsDirectoryURL().appendingPathComponent(Path.Stock.rawValue).path
        return NSKeyedArchiver.archiveRootObject(stockObjects, toFile: file)
    }
   
    static func loadStocksArray() -> [Stock]? {
        let file = documentsDirectoryURL().appendingPathComponent(Path.Stock.rawValue).path
        let result = NSKeyedUnarchiver.unarchiveObject(withFile: file)
        return (result as? [StockClass])?.map{$0.stock}
    }
}

let stocksArray = [
    Stock(companyName: "Tesla", symbol: "TSLA", price: 200.01),
    Stock(companyName: "Apple", symbol: "AAPL", price: 120.12)
]

if
    Stock.saveStocksArray(stocksArray: stocksArray),
    let unarchivedStocks = Stock.loadStocksArray()
{
    print(unarchivedStocks)
}