DesignPatterns是如何使用常用设计模式及示例。
示例：
class MoneyPile { let value: Int var quantity: Int var nextPile: MoneyPile? init(value: Int, quantity: Int, nextPile: MoneyPile?) { self.value = value self.quantity = quantity self.nextPile = nextPile } func canWithdraw(var v: Int) -> Bool { func canTakeSomeBill(want: Int) -> Bool { return (want / self.value) > 0 } var q = self.quantity while canTakeSomeBill(v) { if (q == 0) { break } v -= self.value q -= 1 } if v == 0 { return true } else if let next = self.nextPile { return next.canWithdraw(v) } return false }}class ATM { private var hundred: MoneyPile private var fifty: MoneyPile private var twenty: MoneyPile private var ten: MoneyPile private var startPile: MoneyPile { return self.hundred } init(hundred: MoneyPile, fifty: MoneyPile, twenty: MoneyPile, ten: MoneyPile) { self.hundred = hundred self.fifty = fifty self.twenty = twenty self.ten = ten } func canWithdraw(value: Int) -> String { return "Can withdraw: \(self.startPile.canWithdraw(value))" }}
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