protection_proxy.swift

/*:
☔ 保护代理模式（Protection Proxy）
------------------

在代理模式中，创建一个类代表另一个底层类的功能。
保护代理用于限制访问。

### 示例：
*/
protocol DoorOpening {
    func open(doors: String) -> String
}

final class HAL9000: DoorOpening {
    func open(doors: String) -> String {
        return ("HAL9000: Affirmative, Dave. I read you. Opened \(doors).")
    }
}

final class CurrentComputer: DoorOpening {
    private var computer: HAL9000!

    func authenticate(password: String) -> Bool {

        guard password == "pass" else {
            return false
        }

        computer = HAL9000()

        return true
    }

    func open(doors: String) -> String {

        guard computer != nil else {
            return "Access Denied. I'm afraid I can't do that."
        }

        return computer.open(doors: doors)
    }
}
/*:
### 用法
*/
let computer = CurrentComputer()
let podBay = "Pod Bay Doors"

computer.open(doors: podBay)

computer.authenticate(password: "pass")
computer.open(doors: podBay)