ptr::ptr
Constructs a com::ptr to wrap a COM object.
ptr();
ptr(
_interface_type * p
);
Parameters
- P
A COM interface pointer.
Remarks
The no-argument constructor assigns nullptr to the underlying object handle. Subsequent calls to the com::ptr will validate the internal object and silently fail until an object is actually created or attached.
The one-argument constructor adds a reference to the COM object but does not release the caller's reference, so the caller must call Release on the COM object to truly give up control. When the com::ptr's destructor is called it will automatically release its references on the COM object.
Passing NULL to this constructor is the same as calling the no-argument version.
Example
This example implements a CLR class that uses a com::ptr to wrap its private member IXMLDOMDocument object. It demonstrates usage of both versions of the constructor.
// comptr_ptr.cpp
// compile with: /clr /link msxml2.lib
#include <msxml2.h>
#include <msclr\com\ptr.h>
#import <msxml3.dll> raw_interfaces_only
using namespace System;
using namespace System::Runtime::InteropServices;
using namespace msclr;
// a ref class that uses a com::ptr to contain an
// IXMLDOMDocument object
ref class XmlDocument {
public:
// construct the internal com::ptr with a null interface
// and use CreateInstance to fill it
XmlDocument(String^ progid) {
m_ptrDoc.CreateInstance(progid);
}
// construct the internal com::ptr with a COM object
XmlDocument(IXMLDOMDocument* pDoc) : m_ptrDoc(pDoc) {}
// note that the destructor will call the com::ptr destructor
// and automatically release the reference to the COM object
private:
com::ptr<IXMLDOMDocument> m_ptrDoc;
};
// use the ref class to handle an XML DOM Document object
int main() {
IXMLDOMDocument* pDoc = NULL;
try {
// create an XML DOM document object
Marshal::ThrowExceptionForHR(CoCreateInstance(CLSID_DOMDocument30, NULL,
CLSCTX_ALL, IID_IXMLDOMDocument, (void**)&pDoc));
// construct the ref class with the COM object
XmlDocument doc1(pDoc);
// or create the class from a progid string
XmlDocument doc2("Msxml2.DOMDocument.3.0");
}
// doc1 and doc2 destructors are called when they go out of scope
// and the internal com::ptr releases its reference to the COM object
catch (Exception^ e) {
Console::WriteLine(e);
}
finally {
if (NULL != pDoc) {
pDoc->Release();
}
}
}
Requirements
Header file <msclr\com\ptr.h>
Namespace msclr::com