ios - 如何在 Swift 中对两种类型进行协议(protocol)扩展约束

Question

我有一个协议(protocol)及其相应的扩展，看起来像这样:

import Foundation


protocol HelpActionManageable {
    typealias ItemType : UIViewController,HelpViewControllerDelegate
    var viewController : ItemType {
        get
    }
}

extension HelpActionManageable  {
    func presentHelpViewController() {
        let helpViewController = HelpViewController(nibName: HelpViewController.nibName(), bundle: nil)
        viewController.presentViewController(helpViewController, animated: true, completion:nil)
        helpViewController.delegate = viewController
    }
    func dismissSuccessfulHelpViewController(helpViewController:HelpViewController) {
        helpViewController.dismissViewControllerAnimated(true) { () -> Void  in
            self.viewController.showAlertControllerWithTitle(GlobalConstants.Strings.SUCCESS, message: GlobalConstants.Strings.VALUABLE_FEEDBACK, actions: [], dismissingActionTitle: GlobalConstants.Strings.OK, dismissBlock: nil)
        }
    }
}

因此，在确认此协议(protocol)的随机 View Controller 中，我正在做这样的事情:

class RandomViewController : UIViewController, HelpViewControllerDelegate,HelpActionManageable {
    //HelpViewControllerDelegate methods...
    var viewController : RandomViewController {
        return self
    }
}

这工作正常，但如果扩展 HelpActionManageable 方法仅适用于确认 UIViewController 和 HelpViewControllerDelegate 的类型，那将非常整洁.

是这样的:

extension HelpActionManageable where Self == ItemType

这行不通。我如何在 Swift 中实现这一目标？

Answer 1

我认为现在支持了。

extension HelpActionManageable where Self == ItemType  {
}

或

extension HelpActionManageable where Self: ItemType  {
}

对我有用。