An example service that reads from UserDefaults on init

ExampleServicer.swift

class ExampleService {
  private let userDefaults: UserDefaults
  var aStoredClass: SomeClass
  
  init(userDefaults: UserDefaults) {
    self.userDefaults = userDefaults
    if let serialisedObject = self.userDefaults.object(forKey: "someKey") as? Data {
      if let storedClass = try? JSONDecoder().decode(SomeClass.self, from: serialisedObject) {
        self.aStoredClass = storedClass
    } else {
      self.aStoredClass = SomeClass()
    }
  }
  
  doSomething(newValue: SomeClass) {
    if let serialisedObject = try? JSONEncoder().encode(self.aStoredClass) {
      self.userDefaults.set(serialisedObject, forKey: "someKey")
    }
  }
}