1 析構過程原理

每個類最多只能有一個析構器，而且析構器不帶任何參數(shù)

析構器是在實例釋放發(fā)生前被自動調用。不能主動調用析構器。

子類繼承了父類的析構器，并且在子類析構器實現(xiàn)的最后，父類的析構器會被自動調用。

2 析構器實踐

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