【Swift學習】Swift編程之旅---析構方法（十九）

　　在一個類的實例記憶體被釋放之前，析構方法被立即調用。使用deinit關鍵字來聲明析構方法，類似於構造方法用init來聲明。析構方法只適用於類類型。

deinit { 
   // 析構
 } 

struct Bank { 
    static var coinsInBank = 10_000 
    static func vendCoins(var numberOfCoinsToVend: Int) -> Int { 
       numberOfCoinsToVend = min(numberOfCoinsToVend, coinsInBank) 
       coinsInBank -= numberOfCoinsToVend 
       return numberOfCoinsToVend 
    } 
    static func receiveCoins(coins: Int) { 
    coinsInBank += coins 
   } 
  } 

class Player { 
        var coinsInPurse: Int 
        init(coins: Int) { 
             coinsInPurse = Bank.vendCoins(coins) 
        } 
         func winCoins(coins: Int) { 
             coinsInPurse += Bank.vendCoins(coins) 
        } 
         deinit { 
           Bank.receiveCoins(coinsInPurse) 
        } 
      } 

var playerOne: Player? = Player(coins: 100) 
println("A new player has joined the game with \ (playerOne!.coinsInPurse) coins") 
// 輸出 "A new player has joined the game with 100     coins" 
println("There are now \(Bank.coinsInBank) coins left    in the bank") 
// 輸出 "There are now 9900 coins left in the bank" 

playerOne!.winCoins(2_000) 
println("PlayerOne won 2000 coins & now has \    (playerOne!.coinsInPurse) coins") 
// 輸出 "PlayerOne won 2000 coins & now has 2100 coins" 
println("The bank now only has \(Bank.coinsInBank) coins left") 
// 輸出 "The bank now only has 7900 coins left" 

playerOne = nil 
println("PlayerOne has left the game") 
// 輸出 "PlayerOne has left the game" 
println("The bank now has \(Bank.coinsInBank) coins") 
// 輸出 "The bank now has 10000 coins"