스위프트로 작성된 메멘토

import XCTest /// The Originator holds some important state that may change over time. It also /// defines a method for saving the state inside a memento and another method /// for restoring the state from it. class Originator { /// For the sake of simplicity, the originator's state is stored inside a /// single variable. private var state: String init(state: String) { self.state = state print("Originator: My initial state is: \(state)") } /// The Originator's business logic may affect its internal state. /// Therefore, the client should backup the state before launching methods /// of the business logic via the save() method. func doSomething() { print("Originator: I'm doing something important.") state = generateRandomString() print("Originator: and my state has changed to: \(state)") } private func generateRandomString() -> String { return String(UUID().uuidString.suffix(4)) } /// Saves the current state inside a memento. func save() -> Memento { return ConcreteMemento(state: state) } /// Restores the Originator's state from a memento object. func restore(memento: Memento) { guard let memento = memento as? ConcreteMemento else { return } self.state = memento.state print("Originator: My state has changed to: \(state)") } } /// The Memento interface provides a way to retrieve the memento's metadata, /// such as creation date or name. However, it doesn't expose the Originator's /// state. protocol Memento { var name: String { get } var date: Date { get } } /// The Concrete Memento contains the infrastructure for storing the /// Originator's state. class ConcreteMemento: Memento { /// The Originator uses this method when restoring its state. private(set) var state: String private(set) var date: Date init(state: String) { self.state = state self.date = Date() } /// The rest of the methods are used by the Caretaker to display metadata. var name: String { return state + " " + date.description.suffix(14).prefix(8) } } /// The Caretaker doesn't depend on the Concrete Memento class. Therefore, it /// doesn't have access to the originator's state, stored inside the memento. It /// works with all mementos via the base Memento interface. class Caretaker { private lazy var mementos = [Memento]() private var originator: Originator init(originator: Originator) { self.originator = originator } func backup() { print("\nCaretaker: Saving Originator's state...\n") mementos.append(originator.save()) } func undo() { guard !mementos.isEmpty else { return } let removedMemento = mementos.removeLast() print("Caretaker: Restoring state to: " + removedMemento.name) originator.restore(memento: removedMemento) } func showHistory() { print("Caretaker: Here's the list of mementos:\n") mementos.forEach({ print($0.name) }) } } /// Let's see how it all works together. class MementoConceptual: XCTestCase { func testMementoConceptual() { let originator = Originator(state: "Super-duper-super-puper-super.") let caretaker = Caretaker(originator: originator) caretaker.backup() originator.doSomething() caretaker.backup() originator.doSomething() caretaker.backup() originator.doSomething() print("\n") caretaker.showHistory() print("\nClient: Now, let's rollback!\n\n") caretaker.undo() print("\nClient: Once more!\n\n") caretaker.undo() } } 

Originator: My initial state is: Super-duper-super-puper-super. Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: 1923 Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: 74FB Caretaker: Saving Originator's state... Originator: I'm doing something important. Originator: and my state has changed to: 3681 Caretaker: Here's the list of mementos: Super-duper-super-puper-super. 11:45:44 1923 11:45:44 74FB 11:45:44 Client: Now, let's rollback! Caretaker: Restoring state to: 74FB 11:45:44 Originator: My state has changed to: 74FB Client: Once more! Caretaker: Restoring state to: 1923 11:45:44 Originator: My state has changed to: 1923