ios - 创建一个通用函数，该函数接受 View Controller 类型作为参数，并根据该类型返回自定义 View Controller

Question

我正在尝试创建一个通用函数，它将 View Controller 类型作为参数并返回基于该类型的自定义 View Controller 。

func setUpInstance<T>(_ viewControllerType: T, toName: String?) -> T where T: UIViewController {

        switch viewControllerType {

            case  is GetInstructionsModalViewController:
               let getInstructionsVC = getViewController(GetInstructionsModalViewController.self, "Instructions", identifier: "GetInstructionsVC")
                     getInstructionsVC.delegate = self
                     getInstructionsVC.getDirectionsDelegate = self
                     getInstructionsVC.modalPresentationStyle = .overCurrentContext
                     moveButtonsAccordingToViewHeight(getInstructionsVC.height)

                 return getInstructionsVC as! T

           case is TurnModalViewController:
                let turnVC = getViewController(TurnModalViewController.self, "Turns", identifier: "TurnVC")
                    turnVC.modalPresentationStyle = .overCurrentContext
                    turnVC.delegate = self
                    turnVC.toName = toName
                    bottomContainer.isHidden = true
                    moveButtonsAccordingToViewHeight(turnVC.height)
               return turnVC as! T

           default:
                return UIViewController.self as! T
            }

        }

当我尝试实例化自定义 View Controller 时:

let turnVC = setUpInstance(TurnModalViewController, toName: nil)

我收到错误:

Cannot convert value of type 'TurnByTurnModalViewController.Type' to expected argument type 'UIViewController'

知道如何让这个函数正常工作吗？

Answer 1

看起来您混淆了如何使用泛型。首先，您需要将函数的签名更改为

func setUpInstance<T>(_ viewControllerType: T.Type, toName: String?) -> T where T: UIViewController

因为您想检查输入类型并返回该类型的实例

然后使用正确的参数调用它

let turnVC = setUpInstance(TurnModalViewController.self, toName: nil)