A protocol where can read/write Codable items on disk.

CodableStore.swift

protocol DictionaryStore {
  static var storeFileName: String { get }
  var store: [[String: Any]] { get set }
}

extension DictionaryStore {
  func write() throws {
    let data = try JSONSerialization.data(withJSONObject: store, options: [])
    let document = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let path = document.appendingPathComponent(Self.storeFileName)
    try data.write(to: path)
  }

  func read() throws -> [[String: Any]] {
    let document = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let path = document.appendingPathComponent(Self.storeFileName)
    let data = try Data(contentsOf: path)
    return (try JSONSerialization.jsonObject(with: data, options: []) as? [[String: Any]]) ?? []
  }
}

protocol CodableStore {
  associatedtype StoreType: Codable
  static var storeFileName: String { get }
  var store: [StoreType] { get set }
}

extension CodableStore {
  func write() throws {
    let encoder = JSONEncoder()
    let data = try encoder.encode(store)
    let document = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let path = document.appendingPathComponent(Self.storeFileName)
    try data.write(to: path)
  }

  func read() throws -> [StoreType] {
    let decoder = JSONDecoder()
    let document = try FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false)
    let path = document.appendingPathComponent(Self.storeFileName)
    let data = try Data(contentsOf: path)
    return try decoder.decode([StoreType].self, from: data)
  }
}