Swift设计模式之备忘录模式

// 备忘录模式
// 百度百科：在不破坏封闭的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到原先保存的状态
// 设计模式分类：行为型模式

import Foundation
typealias Memento = Dictionary<NSObject, AnyObject>

let DPMementoKeyChapter = "com.valve.halflife.chapter"
let DPMementoKeyWeapon = "com.valve.halflife.weapon"
let DPMementoGameState = "com.valve.halflife.state"

/// 游戏状态
class GameState {
var chapter: String = ""
var weapon: String = ""

/**
生成游戏存档

- returns: 存档
*/
func toMemento() -> Memento {
return [ DPMementoKeyChapter:chapter, DPMementoKeyWeapon:weapon ]
}

/**
恢复游戏存档

- parameter memento: 存档
*/
func restoreFromMemento(memento: Memento) {
chapter = memento[DPMementoKeyChapter] as? String ?? "n/a"
weapon = memento[DPMementoKeyWeapon] as? String ?? "n/a"
}
}

/**
存档点
*/
enum CheckPoint {
/**
保存存档

- parameter memento: 存档
- parameter keyName: 存档名
*/
static func saveState(memento: Memento, keyName: String = DPMementoGameState) {
//        let defaults = NSUserDefaults.standardUserDefaults()
//        defaults.setObject(memento, forKey: keyName)
//        defaults.synchronize()

DB.set(keyName, obj: memento)
}

/**
读取存档

- parameter keyName: 存档名

- returns: 存档
*/
static func restorePreviousState(keyName keyName: String = DPMementoGameState) -> Memento {
//        let defaults = NSUserDefaults.standardUserDefaults()
//
//        return defaults.objectForKey(keyName) as? Memento ?? Memento()

let m = DB.get(keyName)
return m as? Memento ?? Memento()
}
}

class DB {
static var dict:Dictionary<String, AnyObject> = [:]

class func set(key: String, obj: AnyObject) {
dict[key] = obj
}

class func get(key: String) -> AnyObject? {
return dict[key]
}
}

func printGameStateInfo(state: GameState) -> Void {
print("当前游戏状态：[chapter = \(state.chapter), weapon = \(state.weapon)]")
}

var gameState = GameState()
gameState.restoreFromMemento(CheckPoint.restorePreviousState()) // 新游戏

printGameStateInfo(gameState)

gameState.chapter = "第一章 新手上路"
gameState.weapon = "木剑"
CheckPoint.saveState(gameState.toMemento()) // 第一个存档

printGameStateInfo(gameState)

gameState.chapter = "第二章 冒险开始"
gameState.weapon = "铜剑"
gameState.restoreFromMemento(CheckPoint.restorePreviousState()) // 恢复存档

printGameStateInfo(gameState)

gameState.chapter = "第三章 挑战魔龙"
gameState.weapon = "铁剑"
CheckPoint.saveState(gameState.toMemento(), keyName: "gameState2") // 第二个存档

printGameStateInfo(gameState)

gameState.chapter = "最后章 最终之战"
gameState.weapon = "圣剑"
CheckPoint.saveState(gameState.toMemento()) // 覆盖第一个存档

printGameStateInfo(gameState)

gameState.restoreFromMemento(CheckPoint.restorePreviousState(keyName: "gameState2")) // 加载第二个存档

printGameStateInfo(gameState)