我們要建立一個檔案叫做BaseViewController，點開專案 -> New File -> 選擇Swift檔案並命名為 BaseViewController.swift -> Enter

之後我們建立的ViewController都會繼承BaseViewController，這樣做的意義在於幫助我把程式碼變得更乾淨簡潔！

以下是簡單的跳頁例子：

self.navigationController?.pushViewController(nextVC, animated: animated)

應該都有印象吧？麻煩的點在於，我每次要跳頁，都要寫這一段，如果我寫成一個func，需要用到時把他呼叫出來是不是就方便很多？

public func pushViewController(nextVC: UIViewController, animated: Bool = true) {
    self.navigationController?.pushViewController(nextVC, animated: animated)
}

把上面的寫法改成呼叫func的方式並且讓其他畫面去繼承我的BaseViewController，我要換頁的時候只需要：

pushViewController(nextVC: 你要的ViewController)

事情就簡單很多了，程式碼也會比較乾淨對吧？

接下來把需要用到的都寫進去吧！

/// NavigationController.pushViewController 跳頁 (不帶 Closure)
///
/// 一般常見的 self.navigationController.pushViewController
///
/// - Parameters:
///   - nextVC: 要跳頁到的 UIViewController
///   - animated: 是否要換頁動畫，預設為 true
public func pushViewController(nextVC: UIViewController, animated: Bool = true) {
    self.navigationController?.pushViewController(nextVC, animated: animated)
}

/// NavigationController.pushViewController 跳頁 (不帶 Closure)
///
/// 用 UIApplication.shared.connectScenes 裡面第一個是 keyWindow 的 rootViewController 來當作 UINavigationController，來進行 pushViewController
///
/// - Parameters:
///   - viewController: 要跳頁到的 UIViewController
///   - animated: 是否要換頁動畫，預設為 true
public func pushViewController(_ viewController: UIViewController, animated: Bool = true) {
    if let navigationController = UIApplication.shared
        .connectedScenes
        .compactMap({ $0 as? UIWindowScene })
        .flatMap({ $0.windows })
        .first(where: { $0.isKeyWindow })?
        .rootViewController as? UINavigationController {
        navigationController.pushViewController(viewController, animated: animated)
    }
}

/// NavigationController.pushViewController 跳頁 (帶 Closure)
/// - Parameters:
///   - viewController: 要跳頁到的 UIViewController
///   - animated: 是否要換頁動畫
///   - completion: 換頁過程中，要做的事
public func pushViewController(_ viewController: UIViewController,
                               animated: Bool,
                               completion: @escaping () -> Void) {
    self.navigationController?.pushViewController(viewController, animated: animated)
    guard animated, let coordinator = transitionCoordinator else {
        DispatchQueue.main.async { completion() }
        return
    }
    coordinator.animate(alongsideTransition: nil) { _ in completion() }
}

/// NavigationController.pushViewController 跳頁時刪掉舊的畫面 (不帶 Closure)
/// - Parameters:
///   - currentVC: 現在的 UIViewController
///   - nextVC: 要跳頁到的 UIViewController
///   - animated: 是否要換頁動畫
public func pushViewController(currentVC: UIViewController,
                               nextVC: UIViewController,
                               animated: Bool) {
    navigationController?.pushViewController(nextVC, animated: true)

    guard self.navigationController != nil &&
            self.navigationController?.viewControllers != nil else {
        return
    }

    // 刪除上一個畫面
    let arrayVC = NSMutableArray(array: (self.navigationController?.viewControllers)!)
    for vc in arrayVC {
        if (vc as! UIViewController) == currentVC  {
            arrayVC.remove(vc)
            break
        }
    }

    self.navigationController?.viewControllers = arrayVC as! [UIViewController]
}

/// NavigationController.pushViewController 跳頁時刪掉舊的畫面 (帶 Closure)
/// - Parameters:
///   - currentVC: 現在的 UIViewController
///   - nextVC: 要跳頁到的 UIViewController
///   - animated: 是否要換頁動畫
///   - completion: 換頁過程中，要做的事
public func pushViewController(currentVC: UIViewController,
                               nextVC: UIViewController,
                               animated: Bool,
                               completion: @escaping () -> Void) {
    navigationController?.pushViewController(nextVC, animated: true)

    guard self.navigationController != nil &&
            self.navigationController?.viewControllers != nil else {
        return
    }

    // 刪除上一個畫面
    let arrayVC = NSMutableArray(array: (self.navigationController?.viewControllers)!)
    for vc in arrayVC {
        if (vc as! UIViewController) == currentVC  {
            arrayVC.remove(vc)
            break
        }
    }

    self.navigationController?.viewControllers = arrayVC as! [UIViewController]

    guard animated, let coordinator = transitionCoordinator else {
        DispatchQueue.main.async {
            completion()
        }
        return
    }

    coordinator.animate(alongsideTransition: nil) { _ in
        completion()
    }
}

/// NavigationController.popViewController 回上一頁 (不帶 Closure)
/// - Parameters:
///   - animated: 是否要換頁動畫，預設為 true
public func popViewController(_ animated: Bool = true) {
    self.navigationController?.popViewController(animated: animated)
}

/// NavigationController.popViewController 回上一頁 (帶 Closure)
/// - Parameters:
///   - animated: 是否要換頁動畫
///   - completion: 換頁過程中，要做的事
public func popViewController(animated: Bool, completion: @escaping () -> Void) {
    self.navigationController?.popViewController(animated: animated)
    guard animated, let coordinator = transitionCoordinator else {
        DispatchQueue.main.async { completion() }
        return
    }
    coordinator.animate(alongsideTransition: nil) { _ in completion() }
}

/// NavigationController.popToViewController 回到指定 ViewController (不帶 Closure)
/// - Parameters:
///   - currentVC: 目前所在的 ViewController
///   - popVC_index: 在 NavigationController.viewControllers 中，指定 ViewController 的 index
///   - animated: 是否要換頁動畫，預設為 true
public func popToViewController(currentVC viewController: UIViewController,
                                popVC_index: Int,
                                animated: Bool = true) {
    guard let currentVC_index = navigationController?.viewControllers.firstIndex(of: self) else { return }
    if let vc = navigationController?.viewControllers[currentVC_index - popVC_index] {
        self.navigationController?.popToViewController(vc, animated: animated)
    }
}

/// NavigationController.popToViewController 回到指定 ViewController (不帶 Closure)
///
/// 一般常見的 self.navigationController?.popToViewController
///
/// - Parameters:
///   - viewController: 要 pop 回去的 ViewController
///   - animated: 是否要換頁動畫，預設為 true
public func popToViewController(_ viewController: UIViewController,
                                animated: Bool = true) {
    self.navigationController?.popToViewController(viewController, animated: animated)
}

/// NavigationController.popToViewController 回到指定 ViewController (帶 Closure)
/// - Parameters:
///   - viewController: 要 pop 回去的 ViewController
///   - animated: 是否要換頁動畫
///   - completion: 換頁過程中，要做的事
public func popToViewController(_ viewController: UIViewController,
                                animated: Bool,
                                completion: @escaping () -> Void) {
    self.navigationController?.popToViewController(viewController, animated: animated)
    guard animated, let coordinator = transitionCoordinator else {
        DispatchQueue.main.async { completion() }
        return
    }
    coordinator.animate(alongsideTransition: nil) { _ in completion() }
}

/// NavigationController.popToRootViewController 回到 Root ViewController
/// - Parameters:
///   - animated: 是否要換頁動畫，預設為 true
public func popToRootViewController(_ animated: Bool = true) {
    self.navigationController?.popToRootViewController(animated: animated)
}

/// NavigationController.dismiss (帶 Closure)
/// - Parameters:
///   - animated: 是否要關閉動畫，預設為 true
///   - completion: 關閉過程中，要做的事，預設為 nil
public func dismissViewController(_ animated: Bool = true, completion: (()-> Void)? = nil) {
    self.navigationController?.dismiss(animated: animated, completion: completion)
}

/// ViewController.popUp (帶 Closure)
/// - Parameters:
///   - viewController: 要彈出的 ViewController
///   - modalPresentationStyle: UIModalPresentationStyle，預設為 .overFullScreen
///   - modalTransitionStyle: UIModalTransitionStyle，預設為 .coverVertical
///   - animated: 是否要彈出動畫，預設為 true
///   - completion: 彈出過程中，要做的事，預設為 nil
public func popUpViewController(viewController: UIViewController,
                                modalPresentationStyle: ModalPresentationStyle = .overFullScreen,
                                modalTransitionStyle: ModalTransitionStyle = .coverVertical,
                                animated: Bool = true,
                                completion: (()-> Void)? = nil) {
    viewController.modalPresentationStyle = modalPresentationStyle
    viewController.modalTransitionStyle = modalTransitionStyle
    self.present(viewController, animated: animated, completion: completion)
}

/// ViewController.dismissPopUp
/// - Parameters:
///   - animated: 是否要關閉動畫，預設為 true
///   - completion: 關閉過程中，要做的事，預設為 nil
public func dismissPopUpViewController(_ animated: Bool = true, completion: (()-> Void)? = nil) {
    self.dismiss(animated: animated, completion: completion)
}

/// 清除 NavigationStack 中除了下一個畫面以外的畫面
/// - Parameters:
///   - viewController: 下一個畫面的 ViewController
public func cleanViewControllers(viewController: UIViewController) {
    guard viewController.navigationController?.viewControllers != nil else {
        return
    }
    var vcs = viewController.navigationController!.viewControllers
    for _ in 0 ..< vcs.count - 1 {
        vcs.remove(at: 0)
    }
    DispatchQueue.main.async {
        viewController.navigationController!.viewControllers = vcs
    }
}

以上就是今天的內容！明天見！