内存调试器与LLDB对UINavigationController子控制器数量描述矛盾

内存调试器显示某UINavigationController实例包含1个ContactsTableViewController类型的子控制器，但在LLDB命令行中查询该导航控制器的viewControllers属性时，返回的数组元素数为0。

更新说明 #

• 捕获内存图与执行po命令期间未执行其他操作。
• 以下是可复现该问题的Playground最小代码（仅在使用UIViewControllerRepresentable.Coordinator时会触发此异常）：

import PlaygroundSupport
import SwiftUI
import UIKit

protocol Coordinator {
    var nav: UINavigationController { get }
    func start()
}

final class FlowCoordinator: Coordinator {
    struct Dependencies {
        let nav: UINavigationController
        let screen1Factory: () -> UIViewController
        let screen2Factory: () -> UIViewController
    }

    var nav: UINavigationController
    let screen1Factory: () -> UIViewController
    let screen2Factory: () -> UIViewController

    init(dependencies: FlowCoordinator.Dependencies) {
        self.nav = dependencies.nav
        self.screen1Factory = dependencies.screen1Factory
        self.screen2Factory = dependencies.screen2Factory
    }

    func start() {
        let vc = screen1Factory() as! ViewController
        vc.flowCoordinator = self
        nav.pushViewController(vc, animated: false)
        print("FlowCoordinator.started: flowCoordinator.nav: ", nav, "VCs count: ", nav.viewControllers.count)
    }

    func screen2() {
        print("Pushing screen2")
        let vc = screen2Factory() as! ViewController
        vc.flowCoordinator = self
        nav.pushViewController(vc, animated: false)
        print("Coordinator.viewController.flowCoordinator.nav: ", "VCs count: ",
              nav.viewControllers.count)
    }
}

final class ViewController: UITableViewController {
    weak var flowCoordinator: FlowCoordinator?

    // 表格视图要展示的城市数组
    let cities = ["New York", "Paris", "Tokyo"]

    init() {
        super.init(nibName: nil, bundle: nil)

    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "CityCell")
    }

    // MARK: - 表格视图数据源

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // 返回分区的行数
        return cities.count
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "CityCell", for: indexPath)
        // 配置单元格
        cell.textLabel?.text = cities[indexPath.row]

        return cell
    }

    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        flowCoordinator?.screen2()
    }
}

final class AppDependencies {
    lazy var flowCoordinator: FlowCoordinator = {
        let navigationController = UINavigationController()
        navigationController.navigationBar.prefersLargeTitles = true
        let flowCoordinatorDependencies = FlowCoordinator.Dependencies(
            nav: navigationController,
            screen1Factory: makeViewController1,
            screen2Factory: makeViewController2)
        return FlowCoordinator(dependencies: flowCoordinatorDependencies)
    }()

    func makeViewController1() -> UIViewController {
        let vc = ViewController()
        vc.title = "View 1"
        return vc
    }

    func makeViewController2() -> UIViewController {
        let vc = ViewController()
        vc.title = "View 2"
        return vc
    }
}


struct View1: UIViewControllerRepresentable {
    let flowCoordinator: FlowCoordinator

    func makeUIViewController(context: Context) -> ViewController {
        return context.coordinator.viewController
    }

    func updateUIViewController(_ uiViewController: ViewController, context: Context) {
    }
}

extension View1 {
    final class Coordinator: NSObject, UITableViewDelegate {
        var viewController: ViewController
        var flowCoordinator: FlowCoordinator
        init(flowCoordinator: FlowCoordinator) {
            self.flowCoordinator = flowCoordinator
            self.flowCoordinator.start()
            self.viewController = self.flowCoordinator.nav.viewControllers.first as! ViewController
            super.init()
            viewController.tableView.delegate = self
        }

        func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
            print("View1.tableView(_:didSelectRowAt:indexPath)")
            print("Coordinator.viewController.flowCoordinator.nav: ", viewController.flowCoordinator?.nav ?? "nil", "VCs count: ",
                  viewController.flowCoordinator?.nav.viewControllers.count ?? "nil")
            viewController.flowCoordinator?.screen2()
        }
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator(flowCoordinator: flowCoordinator)
    }
}


struct ContentView: View {
    let deps = AppDependencies()
    var body: some View {
        View1(flowCoordinator: deps.flowCoordinator)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}


let deps = AppDependencies()
//deps.flowCoordinator.start()
let nav = deps.flowCoordinator.nav
//let host = nav
let host = UIHostingController(rootView:   View1(flowCoordinator: deps.flowCoordinator) )
PlaygroundPage.current.liveView = host

内容的提问来源于stack exchange，提问作者onthemoon