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POSome questions about using CComPtr (when use Release()? Can I return CComPtr?, ...)
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  1. POSome questions about using CComPtr (when use Release()? Can I return CComPtr?, ...)
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    copied!<p>I writing add-on for Internet Explorer(BHO) and I'm using CComPtr smart pointers. I wonder:</p> <ol> <li> When should I use CComPtr.Release() function? </li><br> In this <a href="http://msdn.microsoft.com/en-us/library/bb250489%28VS.85%29.aspx" rel="noreferrer">this</a> link it's used to release browser object. Where else should I use it? In 'normal' use (with my own classes) I don't need it. Should I use it in this situation:<br> I get document object using m_spWebBrowser->get_Document(&spDispDoc): <pre> void STDMETHODCALLTYPE CHelloWorldBHO::OnDocumentComplete(IDispatch *pDisp, VARIANT *pvarURL) { // Query for the IWebBrowser2 interface. CComQIPtr spTempWebBrowser = pDisp; // Is this event associated with the top-level browser? if (spTempWebBrowser && m_spWebBrowser && m_spWebBrowser.IsEqualObject(spTempWebBrowser)) { // Get the current document object from browser... CComPtr spDispDoc; <b>hr = m_spWebBrowser->get_Document(&spDispDoc);</b> if (SUCCEEDED(hr)) { // ...and query for an HTML document. CComQIPtr htmlDoc2 = spDispDoc; <b>m_spHTMLDocument = spHTMLDoc;</b> } } } </pre> Should I release spHTMLDocument in SetSite function like I do with m_spWebBrowser (like in link mentioned before)? <li>Can I return CComPtr from a function safely?</li> I mean like this: <pre> CComPtr getObjects(CComQIPtr&lt;IHTMLDocument3&gt; htmlDoc3) { CComPtr objects; hr = htmlDoc3->getElementsByTagName(CComBSTR(L"object"), &objects); if(SUCCEEDED(hr) && objects != NULL) { return objects; } return NULL; } </pre> <li>Should I never use normal pointer?</li> In previous link RemoveImages private function is declared this way: <pre>void RemoveImages(IHTMLDocument2 *pDocument); </pre> but invoked with smart pointer: <pre> CComQIPtr&lt;IHTMLDocument2&gt; spHTMLDoc = spDispDoc; if (spHTMLDoc != NULL) { // Finally, remove the images. RemoveImages(spHTMLDoc); } </pre> I would rather write it this way: <pre>void RemoveImages(CComPtr&lt;IHTMLDocument2&gt; document2);</pre> Is it better? </ol>
 

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