[C++] Page destructor not called on exit

[nlogozzo]

I have an app with a NavigationView and two pages: home and settings.

My settings page is implemented as follows:

#include "pch.h"
#include "SettingsPage.xaml.h"
#if __has_include("SettingsPage.g.cpp")
#include "SettingsPage.g.cpp"
#endif

using namespace ::NickvisionTagger::Models;
using namespace winrt;
using namespace Microsoft::UI::Xaml;
using namespace Microsoft::UI::Xaml::Controls;
using namespace Windows::Foundation;
using namespace Windows::System;

namespace winrt::NickvisionTagger::implementation
{
    SettingsPage::SettingsPage()
    {
        InitializeComponent();
        switch (m_configuration.getTheme())
        {
        case Theme::Light:
            BtnThemeLight().IsChecked(true);
            break;

        case Theme::Dark:
            BtnThemeDark().IsChecked(true);
            break;

        case Theme::System:
            BtnThemeSystem().IsChecked(true);
            break;
        }
        ChkIncludeSubfolders().IsChecked(m_configuration.includeSubfolders());
        ChkRememberLastOpenedMusicFolder().IsChecked(m_configuration.rememberLastMusicFolder());
    }

    SettingsPage::~SettingsPage()
    {
        if (BtnThemeLight().IsChecked().GetBoolean())
        {
            m_configuration.setTheme(Theme::Light);
        }
        else if (BtnThemeDark().IsChecked().GetBoolean())
        {
            m_configuration.setTheme(Theme::Dark);
        }
        else if (BtnThemeSystem().IsChecked().GetBoolean())
        {
            m_configuration.setTheme(Theme::System);
        }
        m_configuration.setIncludeSubfolders(ChkIncludeSubfolders().IsChecked().GetBoolean());
        m_configuration.setRememberLastMusicFolder(ChkRememberLastOpenedMusicFolder().IsChecked().GetBoolean());
        m_configuration.save();
    }

    IAsyncAction SettingsPage::Changelog(const IInspectable& sender, const RoutedEventArgs& e)
    {
        ContentDialog contentDialog;
        contentDialog.Title(box_value(L"What's New?"));
        contentDialog.Content(box_value(L"- Updated to WindowsAppSDK V1.0 and C++"));
        contentDialog.CloseButtonText(L"OK");
        contentDialog.DefaultButton(ContentDialogButton::Close);
        contentDialog.XamlRoot(BtnThemeLight().XamlRoot());
        co_await contentDialog.ShowAsync();
    }

    IAsyncAction SettingsPage::GitHubRepo(const IInspectable& sender, const RoutedEventArgs& e)
    {
        co_await Launcher::LaunchUriAsync(Uri(L"https://github.com/nlogozzo/NickvisionTagger"));
    }

    IAsyncAction SettingsPage::ReportABug(const IInspectable& sender, const RoutedEventArgs& e)
    {
        co_await Launcher::LaunchUriAsync(Uri(L"https://github.com/nlogozzo/NickvisionTagger/issues/new"));
    }
}

As you can see, I rely on the destructor to save the settings to the configuration file. Now, all this works no problem when I switch pages, i.e go from Settings to Home, the destructor is called. However, if i'm on the settings page and close the application via the X button, the destructor is not called and the settings are not saved.
Why? And how can I ensure that the destructor is called when I click the X.

[andrewleader]

Hi @nlogozzo, the best practice in this case is to save the settings immediately when they're changed (for example, when the user selects light theme, save that setting immediately). That way, if your app crashes or is force closed, the settings will still be saved. Alternatively, you could show the user a "Save" button.

Closing the app via the X button is similar to a force terminate and you shouldn't rely on destructors to be called to save app state.