Navigation vs Modal Full Source-Code

ViewController.swift

//
//  ViewController.swift
//  PushVsModal
//
//  Created by jay on 2021/08/28.
//

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        makeTitle()
    }
    
    @IBAction func pushViewController() {
        let targetViewController = UIViewController.viewControllerFromMainStoryboard(identifier: ViewController.storyboardIdentifier)
        self.navigationController?.pushViewController(targetViewController, animated: true)
    }
    
    @IBAction func popViewController() {
        guard let stackCount = self.navigationController?.viewControllers.count,
              stackCount > 1 else {
            let alert = UIAlertController(title: nil,
                                          message: "더 이상 Pop 동작을\n실행할 수 없습니다.",
                                          preferredStyle: .alert)
            let confirmAction = UIAlertAction(title: "확인",
                                              style: .default,
                                              handler: nil)
            alert.addAction(confirmAction)
            
            self.present(alert, animated: true, completion: nil)
            return
        }
           
        self.navigationController?.popViewController(animated: true)
    }
    
    @IBAction func popToRootViewController() {
        guard let stackCount = self.navigationController?.viewControllers.count,
              stackCount > 1 else {
            let alert = UIAlertController(title: nil,
                                          message: "더 이상 Pop 동작을\n실행할 수 없습니다.",
                                          preferredStyle: .alert)
            let confirmAction = UIAlertAction(title: "확인",
                                              style: .default,
                                              handler: nil)
            alert.addAction(confirmAction)
            
            self.present(alert, animated: true, completion: nil)
            return
        }
           
        self.navigationController?.popToRootViewController(animated: true)
    }
    
    @IBAction func popToGrandParentViewController() {
        guard let navigationVC = self.navigationController,
              navigationVC.viewControllers.count > 2 else {
            let alert = UIAlertController(title: nil,
                                          message: "더 이상 Pop to Grand-Parent 동작을 실행할 수 없습니다.",
                                          preferredStyle: .alert)
            let confirmAction = UIAlertAction(title: "확인",
                                              style: .default,
                                              handler: nil)
            alert.addAction(confirmAction)
            
            self.present(alert, animated: true, completion: nil)
            return
        }
        
        let currentStackCount = navigationVC.viewControllers.count
        let targetViewController = navigationVC.viewControllers[currentStackCount - 3]
           
        self.navigationController?.popToViewController(targetViewController, animated: true)
    }
}

// ViewController 의 Title 작성하는 함수
extension UIViewController {
    func makeTitle() {
        self.title = "Navigation-Stack : \(navigationController?.viewControllers.count ?? 1)"
        
        var stackContents: [String] = []
        if let navigationStack = navigationController?.viewControllers {
            for (index, vc) in navigationStack.enumerated() {
                stackContents.append("\(index) - \(vc)")
            }
        }
        print("Stack :\n\(stackContents.joined(separator: "\n"))\n")
    }
}

// Storyboard 에서 ViewController 를 생성하기 위한 Util 함수들
extension UIViewController {
     static var storyboardIdentifier: String {
         return String(describing: self)
     }
     
     static func viewControllerFromMainStoryboard(identifier: String) -> UIViewController {
         return viewController(storyboardName: "Main", identifiler: identifier)
     }
     
     static func viewController(storyboardName: String, identifiler: String) -> UIViewController {
         let storyboard = UIStoryboard(name: storyboardName, bundle: nil)
         if #available(iOS 13.0, *) {
             return storyboard.instantiateViewController(identifier: identifiler)
         } else {
             return storyboard.instantiateViewController(withIdentifier: identifiler)
         }
     }
}