反初始化函数

//: Playground - noun: a place where people can play

import UIKit

//这里是一个反初始化函数操作的例子。

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)

playerOne?.coinsInPurse

Bank.coinsInBank

playerOne?.winCoins(2_000)

playerOne?.coinsInPurse

Bank.coinsInBank

playerOne = nil

Bank.coinsInBank