- Qt 6.9
- Active Qt
- QAxServer
- QAxAggregated
- Qt 6.9.3 Reference Documentation

# QAxAggregated Class

The QAxAggregated class is an abstract base class for implementations of additional COM interfaces. More...

Header: | `#include <QAxAggregated>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS AxServer)` `target_link_libraries(mytarget PRIVATE Qt6::AxServer)`
qmake: | `QT += axserver`

- List of all members, including inherited members

## Public Functions

virtual long | queryInterface(const QUuid &iid, void **iface) = 0

## Protected Functions

virtual | ~QAxAggregated()
IUnknown * | controllingUnknown() const
QObject * | object() const
QWidget * | widget() const

## Detailed Description

Create a subclass of QAxAggregated and reimplement queryInterface() to support additional COM interfaces. Use multiple inheritance from those COM interfaces. Implement the IUnknown interface of those COM interfaces by delegating the calls to `QueryInterface()`, `AddRef()` and `Release()` to the interface provided by controllingUnknown().

Use the widget() method if you need to make calls to the QWidget implementing the ActiveX control. You must not store that pointer in your subclass (unless you use QPointer), as the QWidget can be destroyed by the ActiveQt framework at any time.

See also QAxBindable, QAxFactory, and Active Qt.

## Member Function Documentation

### `[virtual constexpr noexcept protected]` QAxAggregated::~QAxAggregated()

The destructor is called internally by Qt.

### `[protected]` IUnknown *QAxAggregated::controllingUnknown() const

Returns the `IUnknown` interface of the ActiveX control. Implement the `IUnknown` interface in your QAxAggregated subclass to delegate calls to `QueryInterface()`, `AddRef()`, and `Release()` to the interface provided by this function.

     HRESULT AxImpl::QueryInterface(REFIID iid, void **iface)
     {
         return controllingUnknown()->QueryInterface(iid, iface);
     }

     ulong AxImpl::AddRef()
     {
         return controllingUnknown()->AddRef();
     }

     ulong AxImpl::Release()
     {
         return controllingUnknown()->Release();
     }

Instead of declaring and implementing these three functions manually, you can use the `QAXAGG_IUNKNOWN` macro in the class declaration of your subclass.

### `[protected]` QObject *QAxAggregated::object() const

Returns a pointer to the QObject subclass implementing the COM object. This function might return 0.

Warning: You must not store the returned pointer, unless you use a QPointer, since the QObject can be destroyed by ActiveQt at any time.

### `[pure virtual]` long QAxAggregated::queryInterface(const QUuid &iid, void **iface)

Reimplement this pure virtual function to support additional COM interfaces. Set the value of iface to point to this object to support the interface iid. Note that you must cast the `this` pointer to the appropriate superclass.

     long AxImpl::queryInterface(const QUuid &iid, void **iface)
     {
         *iface = 0;
         if (iid == IID_ISomeCOMInterface)
             *iface = (ISomeCOMInterface*)this;
         else
             return E_NOINTERFACE;

         AddRef();
         return S_OK;
     }

Return the standard COM results `S_OK` (interface is supported) or `E_NOINTERFACE` (requested interface is not supported).

Warning: Even though you must implement the `IUnknown` interface if you implement any COM interface you must not support the `IUnknown` interface in your queryInterface() implementation.

### `[protected]` QWidget *QAxAggregated::widget() const

Returns a pointer to the QWidget subclass implementing the ActiveX control. This function might return 0.

Warning: You must not store the returned pointer, unless you use a QPointer, since the QWidget can be destroyed by ActiveQt at any time.