import Foundation

/*析构过程原理******************************************************/

//Swift 会自动释放不再需要的实例以释放资源。如自动引用计数章节中所讲述,Swift 通过自动引用计数(ARC) 处理实例的内存管理。通常当你的实例被释放时不需要手动地去清理。但是,当使用自己的资源时,你可能 需要进行一些额外的清理。例如,如果创建了一个自定义的类来打开一个文件,并写入一些数据,你可能需要在 类实例被释放之前手动去关闭该文件。

//在类的定义中,每个类最多只能有一个析构器,而且析构器不带任何参数,如下所示:

//deinit {

// // 执行析构过程

//}

//析构器是在实例释放发生前被自动调用。析构器是不允许被主动调用的。子类继承了父类的析构器,并且在子类析构器实现的最后,父类的析构器会被自动调用。即使子类没有提供自己的析构器,父类的析构器也同样会被调用。

/*析构器操作******************************************************/

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)

print("A new player has joined the game with \(playerOne!.coinsInPurse) coins")

// 输出 "A new player has joined the game with 100 coins"

print("There are now \(Bank.coinsInBank) coins left in the bank")

// 输出 "There are now 9900 coins left in the bank"

playerOne!.winCoins(2_000)

print("PlayerOne won 2000 coins & now has \(playerOne!.coinsInPurse) coins")

// 输出 "PlayerOne won 2000 coins & now has 2100 coins"

print("The bank now only has \(Bank.coinsInBank) coins left")

// 输出 "The bank now only has 7900 coins left"

playerOne = nil

print("PlayerOne has left the game")

// 输出 "PlayerOne has left the game"

print("The bank now has \(Bank.coinsInBank) coins")

// 输出 "The bank now has 10000 coins"