Can you have 2 identical COM objects? - c++

Question

A general question that could help answer another question I asked before. I believe that COM objects only return a pointer to the created object. So when I try to initialize a COM object twice, do I make two COM objects in my app, or do I make two different pointers to the same object? or perhaps there are two copies of the object that the pointers point to their respective objects?
// Pointer to WebViewController
static wil::com_ptr<ICoreWebView2Controller> webviewController;
// Pointer to WebView window
static wil::com_ptr<ICoreWebView2> webviewWindow;
// Locate the browser and set up the environment for WebView
CreateCoreWebView2EnvironmentWithOptions(nullptr, nullptr, nullptr,
Callback<ICoreWebView2CreateCoreWebView2EnvironmentCompletedHandler>(
[hWnd, url](HRESULT result, ICoreWebView2Environment* env) -> HRESULT {
// Create a CoreWebView2Controller and get the associated CoreWebView2 whose parent is the main window hWnd
env->CreateCoreWebView2Controller(hWnd, Callback<ICoreWebView2CreateCoreWebView2ControllerCompletedHandler>(
[hWnd, url](HRESULT result, ICoreWebView2Controller* controller) -> HRESULT {
_com_error err4(result);
MessageBoxW(hWnd, L"Controller setup", 0, MB_OK);
MessageBoxW(hWnd, err4.ErrorMessage(), 0, MB_OK);
if (controller != nullptr) {
webviewController = controller;
webviewController->get_CoreWebView2(&webviewWindow);
}
// Add a few settings for the webview
// The demo step is redundant since the values are the default settings
ICoreWebView2Settings* Settings;
webviewWindow->get_Settings(&Settings);
Settings->put_IsScriptEnabled(TRUE);
Settings->put_AreDefaultScriptDialogsEnabled(TRUE);
Settings->put_IsWebMessageEnabled(TRUE);
// Resize WebView to fit the bounds of the parent window
RECT bounds;
GetClientRect(hWnd, &bounds);
webviewController->put_Bounds(bounds);
// Schedule an async task to navigate to Bing
webviewWindow->Navigate(url);
if (GetWindow(hWnd, GW_CHILD) != NULL) {
MessageBoxW(hWnd, L"not a NULL child window", 0, MB_OK);
};
// Step 4 - Navigation events
// Step 5 - Scripting
// Step 6 - Communication between host and web content
return S_OK;
}).Get());
return S_OK;
}).Get());
I called
CoInitialize(NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE); earlier in the code only once. My question is what happens when I run this block twice?

Answer 1

My question is what happens when I run this block twice?
In this specific case, executing the code twice will produce two distinct WebView2 instances. Both instances are then assigned to the same static variable, causing one instance to be irrevocably leaked.
Being an XY Problem this information isn't terribly useful. The real issue you are trying to solve is knowing when the WebView2 control is fully constructed. That question has been answered elsewhere.

Answer 2

So when I try to initialize a COM object twice, do I make two COM objects in my app, or do I make two different pointers to the same object? or perhaps there are two copies of the object that the pointers point to their respective objects?
That really depends on the implementation of the COM object. If it is implemented as a singleton, then instantiating it multiple times will return a pointer to the existing instance (creating a new instance if it doesn't exist yet). But, if the COM object is not implemented as a singleton, then each instantiation will return a pointer to a new instance.