無法將類型“()”的返回表達式轉換為返回類型“T”

Question

需要為在調度主線程中實例化的視圖控制器包裝擴展，但是遇到了那個錯誤，有什么解決辦法嗎？

extension UIStoryboard {

    convenience init(name: StoryboardName) {
        self.init(name: name.rawValue, bundle: nil)
    }

    func instantiateVC<T: UIViewController>(identifier: String = T.identifier) -> T {
        // swiftlint:disable force_cast
        DispatchQueue.main.async {
            let controller = self.instantiateViewController(withIdentifier: identifier) as! T
            controller.removeBackButtonTitle()
            return controller
        }
        // swiftlint:enable force_cast
    }

    func instantiateInitialVC() -> UIViewController {
        return self.instantiateInitialViewController()!
    }
}

Answer 1

instantiateVC不應返回值。 您需要向此函數添加一個新參數以傳遞controller ：

func instantiateVC<T: UIViewController>(identifier: String = T.identifier, completion: @escaping (T) -> Void) {
    // swiftlint:disable force_cast
    DispatchQueue.main.async {
        let controller = self.instantiateViewController(withIdentifier: identifier) as! T
        controller.removeBackButtonTitle()
        completion(controller)
    }
    // swiftlint:enable force_cast
}

Answer 2

試試是否只去掉主線程上的按鈕標題就足夠了

func instantiateVC<T: UIViewController>(identifier: String = T.Identifier) -> T {
    let controller = self.instantiateViewController(withIdentifier: identifier) as! T
    DispatchQueue.main.async {
        controller.removeButtonTitle()
    }
    return controller
}