Defining a smart pointer as a member variable of a class - visual-c++

Question

Header:
CChristianLifeMinistryHtmlView m_pHtmlView = nullptr;
Source:
m_pHtmlView = new CChristianLifeMinistryHtmlView();
Trying to change it to use a smart pointer. I can do this (inside OnInitDialog):
auto m_pHtmlView2 = std::make_unique<CChristianLifeMinistryHtmlView>;
But I can't work out how to have my smart pointer defined as a member variable of my CDialog class. I can't do: std::unique_ptr m_pHtmlView2.
I saw this discussion (Using smart pointers as a class member) and based on that I tried this in the header:
//CChristianLifeMinistryHtmlView *m_pHtmlView;
std::unique_ptr<CChristianLifeMinistryHtmlView> m_pHtmlView;
But that will not compile:
6>C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.30.30704\include\memory(3087,1): error C2248: 'CChristianLifeMinistryHtmlView::~CChristianLifeMinistryHtmlView': cannot access protected member declared in class 'CChristianLifeMinistryHtmlView'
6>D:\My Programs\2022\MeetSchedAssist\Meeting Schedule Assistant\ChristianLifeMinistryHtmlView.h(104): message : compiler has generated 'CChristianLifeMinistryHtmlView::~CChristianLifeMinistryHtmlView' here
6>D:\My Programs\2022\MeetSchedAssist\Meeting Schedule Assistant\ChristianLifeMinistryHtmlView.h(22): message : see declaration of 'CChristianLifeMinistryHtmlView'
6>C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.30.30704\include\memory(3085): message : while compiling class template member function 'void std::default_delete<CChristianLifeMinistryHtmlView>::operator ()(_Ty *) noexcept const'
6> with
6> [
6> _Ty=CChristianLifeMinistryHtmlView
6> ]
6>C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.30.30704\include\memory(3195): message : see reference to function template instantiation 'void std::default_delete<CChristianLifeMinistryHtmlView>::operator ()(_Ty *) noexcept const' being compiled
6> with
6> [
6> _Ty=CChristianLifeMinistryHtmlView
6> ]
6>C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.30.30704\include\memory(3122): message : see reference to class template instantiation 'std::default_delete<CChristianLifeMinistryHtmlView>' being compiled
6>D:\My Programs\2022\MeetSchedAssist\Meeting Schedule Assistant\AvailableBrothersReportPreview.h(52): message : see reference to class template instantiation 'std::unique_ptr<CChristianLifeMinistryHtmlView,std::default_delete<CChristianLifeMinistryHtmlView>>' being compiled
Update
Based on the advice in the comments I now have:
Header:
std::unique_ptr<CChristianLifeMinistryHtmlView> m_pHtmlView;
Source (in OnInitDialog):
m_pHtmlView = std::make_unique<CChristianLifeMinistryHtmlView>();
if (m_pHtmlView != nullptr)
{
m_pHtmlView->Create(nullptr, nullptr, AFX_WS_DEFAULT_VIEW,
m_rctPreviewHtml, this, 0);
m_pHtmlView->ShowWindow(SW_SHOWNORMAL);
if(CMeetingScheduleAssistantApp::WaitForFileToBeReady(m_strTempHtmlFile))
m_pHtmlView->Navigate2(m_strTempHtmlFile, 0, nullptr);
}
It complies and works. My popup dialog displays and the CHtmlView derived control is visible. Cool. But when I click OK to close the dialog I get an exception:
How do we address that?

Answer 1

CHtmlView is derived from CFormView -> CView, which deletes itself in CView::PostNcDestroy with delete this; So the memory is already managed.
Replace new with std::make_unique, and call release() immediately, because you don't want unique_ptr to delete it anymore.
//m_pHtmlView = new CChristianLifeMinistryHtmlView();
m_pHtmlView = std::make_unique<CChristianLifeMinistryHtmlView>().release();
If you had written new and delete in your original code (that also means you at least override CMyHtmlView::PostNcDestroy) then unique_ptr can be used to replace both new and delete.
In this case, you only had new in the original code. You don't want unique_ptr to manage delete