15.反初始化 Deinitialization Swift官方

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

import UIKit

// # define: 类实例被释放时做的额外处理.只对类有效

// 每个类当中只能有一个反初始化器。反初始化器不接收任何形式参数，并且不需要写圆括号

// 不能自行调用反初始化器

// 父类的反初始化器可以被子类继承，并且子类的反初始化器实现结束之后父类的反初始化器会被调用。父类的反初始化器总会被调用，就算子类没有反初始化器。
// 一个游戏
class Bank {
    static var coinsInBank = 10_000
    static func distribute(coins numberOfCoinsRequested: Int) -> Int {
        let numberOfCoinToVend = min(numberOfCoinsRequested, coinsInBank)
        coinsInBank -= numberOfCoinToVend
        return numberOfCoinToVend
    }
    static func receive(coins: Int) {
        coinsInBank += coins
    }
}
class Player {
    var coinsInPurse: Int
    init(coins: Int) {
        coinsInPurse = Bank.distribute(coins: coins)
    }
    func win(coins: Int) {
        coinsInPurse += Bank.distribute(coins: coins)
    }
    deinit {
        print("The player is leaving...")
        Bank.receive(coins: coinsInPurse)
    }
}
var playerOne: Player? = Player(coins: 100)
print("A new player has joined the game with \(playerOne!.coinsInPurse) coins.")
print("There are now \(Bank.coinsInBank) coins left in the bank.")
playerOne!.win(coins: 2_000)
playerOne!.coinsInPurse
Bank.coinsInBank
playerOne = nil
Bank.coinsInBank