Swift 如何在指定的初始值设定项中调用协议扩展初始值设定项？

我试图将协议扩展初始值设定项注入现有类的指定初始值设定项中。我认为如果不重写类中指定的初始值设定项，然后在类中调用协议扩展初始值设定项，就没有办法解决这个问题

下面是我正在尝试的，特别是使用

UIViewController

类：

class FirstViewController: UIViewController, MyProtocol {

    var locationManager: CLLocationManager?
    var lastRendered: NSDate?

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        // TODO: How to call MyProtocol initializer?
        // (self as MyProtocol).init(aDecoder) // Didn't compile
    }

}

protocol MyProtocol: CLLocationManagerDelegate {

    var locationManager: CLLocationManager? { get set }
    var lastRendered: NSDate? { get set }

    init?(coder aDecoder: NSCoder)
}

extension MyProtocol where Self: UIViewController {

    // Possible to inject this into initialization process?
    init?(coder aDecoder: NSCoder) {
        self.init(coder: aDecoder)
        setupLocationManager()
    }

    func setupLocationManager() {
        locationManager = CLLocationManager()
        locationManager?.delegate = self
        locationManager?.desiredAccuracy = kCLLocationAccuracyThreeKilometers
        locationManager?.distanceFilter = 1000.0
        locationManager?.startUpdatingLocation()
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        // TODO
    }

    func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
        // TODO
    }

    func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
        // TODO
    }
}

是否有一种方法可以使用协议扩展初始值设定项，以便在框架现有的初始化过程中自动调用它？

您不需要调用其他初始值设定项；你已经在初始化了。此外，您不需要将

self

强制转换为MyProtocol；您已经声明它采用MyProtocol。另外，您已经将MyProtocol的

setupLocationManager

注入FirstViewController，因为您的FirstViewController已经采用MyProtocol，并且MyProtocol上的扩展针对的是UIViewController，它是FirstViewController的超类

因此，该方法已经被注入；现在只需直接调用您正在运行的初始值设定项中的注入方法。以下精简版本的代码编译得非常好：

class FirstViewController: UIViewController, MyProtocol {
    var locationManager: CLLocationManager?

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.setupLocationManager() // no problem!
    }
}

protocol MyProtocol: CLLocationManagerDelegate {
    // this next line is necessary so that
    // ...setupLocationManager can refer to `self.locationManager`
    var locationManager: CLLocationManager? { get set }
}

extension MyProtocol where Self: UIViewController {
    func setupLocationManager() {
        locationManager = CLLocationManager()
        // ... etc.
    }
    // ... etc.
}