1 析构过程原理
每个类最多只能有一个析构器，而且析构器不带任何参数
析构器是在实例释放发生前被自动调用。不能主动调用析构器。
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。
2 析构器实践
class Bank {
static var coinsInBank = 10_000
static func vendCoins(numberOfCoinsRequested: Int) -> Int {
let numberOfCoinsToVend = min(numberOfCoinsRequested, coinsInBank)
coinsInBank -= numberOfCoinsToVend
return numberOfCoinsToVend
}
static func receiveCoins(coins: Int) {
coinsInBank += coins
}
}
class Player {
var coinsInPurse: Int
init(coins: Int) {
coinsInPurse = Bank.vendCoins(numberOfCoinsRequested: coins)
}
func winCoins(coins: Int) {
coinsInPurse += Bank.vendCoins(numberOfCoinsRequested: coins)
}
deinit {
Bank.receiveCoins(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!.winCoins(coins: 2_000)
print("PlayerOne won 2000 coins & now has \(playerOne!.coinsInPurse) coins")
print("The bank now only has \(Bank.coinsInBank) coins left")
playerOne = nil
print("PlayerOne has left the game")
print("The bank now has \(Bank.coinsInBank) coins")
playground文件在andyRon/LearnSwift
