从 A push 到 B, 从B push 到C, 从C返回直接到A

最佳方案

思路: 在B跳转C后将B从栈中删除
最佳时机: B 跳转 C的push动画完成之后移除

import UIKit

extension UINavigationController {
    
    /// remove spacial UIViewController
    ///
    /// - Parameter aClass: UIViewController Class
    func removeViewController(_ aClass: AnyClass) {
        viewControllers.removeAll(where: { $0.isKind(of: aClass) })
    }
    
    
    /// Push a UIViewController and remove a UIViewController class in the current stack when the push animation finished
    /// - Parameters:
    ///   - controller: A UIViewController instance that will be pushed
    ///   - removeClass: The UIViewController class that needs to be removed, default is nil
    func push(_ controller: UIViewController, removeClass: AnyClass? = nil) {
        CATransaction.setCompletionBlock { [unowned self] in
            // 移除栈中的当前Controller
            if let removeClass = removeClass {
                self.navigationController?.removeViewController(removeClass)
            }
        }
        CATransaction.begin()
        pushViewController(controller, animated: true)
        CATransaction.commit()
    }
}

示例:

import UIKit

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.backgroundColor = .white
        let naviController = UINavigationController(rootViewController: AViewController())
        window?.rootViewController = naviController
        window?.makeKeyAndVisible()
        return true
    }

}

import UIKit

class AViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .brown
        title = "AController"
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        let vc = BViewController()
        navigationController?.pushViewController(vc, animated: true)
    }
}

import UIKit

class BViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .red
        title = "BController"
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        let vc = CViewController()
        navigationController?.push(vc, removeClass: BViewController.self)
    }
}

import UIKit

class CViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        title = "CController"
        view.backgroundColor = .orange
    }
}