QAxBase Class | Active Qt | Qt 6.11.1
Description: The QAxBase class is an abstract class that provides an API to initialize and access a COM object.

- Qt 6.11
- Active Qt
- QAxContainer
- QAxBase
- Qt 6.11.1 Reference Documentation

# QAxBase Class

The QAxBase class is an abstract class that provides an API to initialize and access a COM object. More...

Header: | `#include <QAxBase>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS AxContainer)` `target_link_libraries(mytarget PRIVATE Qt6::AxContainer)`
qmake: | `QT += axcontainer`
Inherited By: | QAxObject and QAxWidget

- List of all members, including inherited members

## Public Types

| PropertyBag

## Public Functions

virtual | ~QAxBase()
QVariant | asVariant() const
ulong | classContext() const
void | clear()
QString | control() const
void | disableClassInfo()
void | disableEventSink()
void | disableMetaObject()
QVariant | dynamicCall(const char *function, const QVariant &var1 = QVariant(), const QVariant &var2 = QVariant(), const QVariant &var3 = QVariant(), const QVariant &var4 = QVariant(), const QVariant &var5 = QVariant(), const QVariant &var6 = QVariant(), const QVariant &var7 = QVariant(), const QVariant &var8 = QVariant())
QVariant | dynamicCall(const char *function, QList<QVariant> &vars)
QString | generateDocumentation()
bool | isNull() const
QAxBase::PropertyBag | propertyBag() const
virtual bool | propertyWritable(const char *prop) const
long | queryInterface(const QUuid &uuid, void **iface) const
QAxObject * | querySubObject(const char *name, const QVariant &var1 = QVariant(), const QVariant &var2 = QVariant(), const QVariant &var3 = QVariant(), const QVariant &var4 = QVariant(), const QVariant &var5 = QVariant(), const QVariant &var6 = QVariant(), const QVariant &var7 = QVariant(), const QVariant &var8 = QVariant())
QAxObject * | querySubObject(const char *name, QList<QVariant> &vars)
void | setClassContext(ulong classContext)
void | setPropertyBag(const QAxBase::PropertyBag &bag)
virtual void | setPropertyWritable(const char *prop, bool ok)
QStringList | verbs() const

## Protected Functions

| QAxBase()
virtual bool | initialize(IUnknown **ptr)
bool | initializeActive(IUnknown **ptr)
bool | initializeFromFile(IUnknown **ptr)
bool | initializeLicensed(IUnknown **ptr)
bool | initializeRemote(IUnknown **ptr)

## Detailed Description

QAxBase is an abstract class that cannot be used directly, and is instantiated through the subclasses QAxObject and QAxWidget. This class provides the API to access the COM object directly through its IUnknown implementation. If the COM object implements the IDispatch interface, the properties and methods of that object become available as Qt properties and slots.

     connect(buttonBack, SIGNAL(clicked()), webBrowser, SLOT(GoBack()));

Properties exposed by the object's IDispatch implementation can be read and written through the property system provided by the Qt Object Model (both subclasses are QObjects, so you can use QObject::setProperty() and QObject::property()). Properties with multiple parameters are not supported.

     activeX->setProperty("text", "some text");
     int value = activeX->property("value");

Write-functions for properties and other methods exposed by the object's IDispatch implementation can be called directly using dynamicCall(), or indirectly as slots connected to a signal.

     webBrowser->dynamicCall("GoHome()");

Outgoing events supported by the COM object are emitted as standard Qt signals.

     connect(webBrowser, SIGNAL(TitleChanged(QString)),
             this, SLOT(setCaption(QString)));

QAxBase transparently converts between COM data types and the equivalent Qt data types. Some COM types have no equivalent Qt data structure.

Supported COM datatypes are listed in the first column of following table. The second column is the Qt type that can be used with the QObject property functions. The third column is the Qt type that is used in the prototype of generated signals and slots for in-parameters, and the last column is the Qt type that is used in the prototype of signals and slots for out-parameters.

COM type | Qt property | in-parameter | out-parameter
--- | --- | --- | ---
VARIANT_BOOL | bool | bool | bool&
BSTR | QString | const QString& | QString&
char, short, int, long | int | int | int&
uchar, ushort, uint, ulong | uint | uint | uint&
float, double | double | double | double&
DATE | QDateTime | const QDateTime& | QDateTime&
CY | qlonglong | qlonglong | qlonglong&
OLE_COLOR | QColor | const QColor& | QColor&
SAFEARRAY(VARIANT) | QList<QVariant> | const QList<QVariant>& | QList<QVariant>&
SAFEARRAY(int), SAFEARRAY(double), SAFEARRAY(Date) | QList<QVariant> | const QList<QVariant>& | QList<QVariant>&
SAFEARRAY(BYTE) | QByteArray | const QByteArray& | QByteArray&
SAFEARRAY(BSTR) | QStringList | const QStringList& | QStringList&
VARIANT | type-dependent | const QVariant& | QVariant&
IFontDisp* | QFont | const QFont& | QFont&
IPictureDisp* | QPixmap | const QPixmap& | QPixmap&
IDispatch* | QAxObject* | `QAxBase::asVariant()` | QAxObject* (return value)
IUnknown* | QAxObject* | `QAxBase::asVariant()` | QAxObject* (return value)
SCODE, DECIMAL | unsupported | unsupported | unsupported
VARIANT* (Since Qt 4.5) | unsupported | QVariant& | QVariant&

Supported are also enumerations, and typedefs to supported types.

To call the methods of a COM interface described by the following IDL

     dispinterface IControl
     {
     properties:
         [id(1)] BSTR text;
         [id(2)] IFontDisp *font;

     methods:
         [id(6)] void showColumn([in] int i);
         [id(3)] bool addColumn([in] BSTR t);
         [id(4)] int fillList([in, out] SAFEARRAY(VARIANT) *list);
         [id(5)] IDispatch *item([in] int i);
     };

use the QAxBase API like this:

     QAxObject object("<CLSID>");

     QString text = object.property("text").toString();
     object.setProperty("font", QFont("Times New Roman", 12));

     connect(this, SIGNAL(clicked(int)), &object, SLOT(showColumn(int)));
     bool ok = object.dynamicCall("addColumn(const QString&)", "Column 1").toBool();

     QList<QVariant> varlist;
     QList<QVariant> parameters;
     parameters << QVariant(varlist);
     int n = object.dynamicCall("fillList(QList<QVariant>&)", parameters).toInt();

     QAxObject *item = object.querySubItem("item(int)", 5);

Note that the QList the object should fill has to be provided as an element in the parameter list of QVariants.

If you need to access properties or pass parameters of unsupported datatypes you must access the COM object directly through its `IDispatch` implementation or other interfaces. Those interfaces can be retrieved through queryInterface().

     IUnknown *iface = 0;
     activeX->queryInterface(IID_IUnknown, (void**)&iface);
     if (iface) {
         // use the interface
         iface->Release();
     }

To get the definition of the COM interfaces you will have to use the header files provided with the component you want to use. Some compilers can also import type libraries using the #import compiler directive. See the component documentation to find out which type libraries you have to import, and how to use them.

If you need to react to events that pass parameters of unsupported datatypes you can use the generic signal that delivers the event data as provided by the COM event.

See also QAxObject, QAxWidget, QAxScript, and ActiveQt Framework.

## Member Type Documentation

### `[alias]` QAxBase::PropertyBag

A QMap<QString,QVariant> that can store properties as name:value pairs.

## Member Function Documentation

### `[protected]` QAxBase::QAxBase()

Creates a QAxBase object.

### `[virtual noexcept]` QAxBase::~QAxBase()

Shuts down the COM object and destroys the QAxBase object.

See also clear().

### QVariant QAxBase::asVariant() const

Returns a QVariant that wraps the COM object. The variant can then be used as a parameter in e.g. dynamicCall().

### ulong QAxBase::classContext() const

Returns the context the ActiveX control will run in (default CLSCTX_SERVER).

See also setClassContext().

### void QAxBase::clear()

Disconnects and destroys the COM object.

If you reimplement this function you must also reimplement the destructor to call clear(), and call this implementation at the end of your clear() function.

### QString QAxBase::control() const

Returns the ActiveX control.

### void QAxBase::disableClassInfo()

Disables the class info generation for this ActiveX container. If you don't require any class information about the ActiveX control use this function to speed up the meta object generation.

Note that this function must be called immediately after construction of the object

### void QAxBase::disableEventSink()

Disables the event sink implementation for this ActiveX container. If you don't intend to listen to the ActiveX control's events use this function to speed up the meta object generation.

Some ActiveX controls might be unstable when connected to an event sink. To get OLE events you must use standard COM methods to register your own event sink. Use queryInterface() to get access to the raw COM object.

Note that this function should be called immediately after construction of the object.

### void QAxBase::disableMetaObject()

Disables the meta object generation for this ActiveX container. This also disables the event sink and class info generation. If you don't intend to use the Qt meta object implementation call this function to speed up instantiation of the control. You will still be able to call the object through dynamicCall(), but signals, slots and properties will not be available with QObject APIs.

Some ActiveX controls might be unstable when used with OLE automation. Use standard COM methods to use those controls through the COM interfaces provided by queryInterface().

Note that this function must be called immediately after construction of the object.

### QVariant QAxBase::dynamicCall(const char *function, const QVariant &var1 = QVariant(), const QVariant &var2 = QVariant(), const QVariant &var3 = QVariant(), const QVariant &var4 = QVariant(), const QVariant &var5 = QVariant(), const QVariant &var6 = QVariant(), const QVariant &var7 = QVariant(), const QVariant &var8 = QVariant())

Calls the COM object's method function, passing the parameters var1, var1, var2, var3, var4, var5, var6, var7 and var8, and returns the value returned by the method, or an invalid QVariant if the method does not return a value or when the function call failed.

If function is a method of the object the string must be provided as the full prototype, for example as it would be written in a QObject::connect() call.

     activeX->dynamicCall("Navigate(const QString&)", "www.qt-project.org");

Alternatively a function can be called passing the parameters embedded in the string, e.g. above function can also be invoked using

     activeX->dynamicCall("Navigate(\"www.qt-project.org\")");

All parameters are passed as strings; it depends on the control whether they are interpreted correctly, and is slower than using the prototype with correctly typed parameters.

If function is a property the string has to be the name of the property. The property setter is called when var1 is a valid QVariant, otherwise the getter is called.

     activeX->dynamicCall("Value", 5);
     QString text = activeX->dynamicCall("Text").toString();

Note that it is faster to get and set properties using QObject::property() and QObject::setProperty().

dynamicCall() can also be used to call objects with a disabled metaobject wrapper, which can improve performance significantely, esp. when calling many different objects of different types during an automation process. ActiveQt will then however not validate parameters.

It is only possible to call functions through dynamicCall() that have parameters or return values of datatypes supported by QVariant. See the QAxBase class documentation for a list of supported and unsupported datatypes. If you want to call functions that have unsupported datatypes in the parameter list, use queryInterface() to retrieve the appropriate COM interface, and use the function directly.

     IWebBrowser2 *webBrowser = 0;
     activeX->queryInterface(IID_IWebBrowser2, (void **)&webBrowser);
     if (webBrowser) {
         webBrowser->Navigate2(pvarURL);
         webBrowser->Release();
     }

This is also more efficient.

### QVariant QAxBase::dynamicCall(const char *function, QList<QVariant> &vars)

Calls the COM object's method function, passing the parameters in vars, and returns the value returned by the method. If the method does not return a value or when the function call failed this function returns an invalid QVariant object.

The QVariant objects in vars are updated when the method has out-parameters.

This is an overloaded function.

### QString QAxBase::generateDocumentation()

Returns a rich text string with documentation for the wrapped COM object. Dump the string to an HTML-file, or use it in e.g. a QTextBrowser widget.

### `[virtual protected]` bool QAxBase::initialize(IUnknown **ptr)

This virtual function is called by setControl() and creates the requested COM object. ptr is set to the object's IUnknown implementation. The function returns true if the object initialization succeeded; otherwise the function returns false.

The default implementation interprets the string returned by control(), and calls initializeRemote(), initializeLicensed() or initializeActive() if the string matches the respective patterns. If control() is the name of an existing file, initializeFromFile() is called. If no pattern is matched, or if remote or licensed initialization fails, CoCreateInstance is used directly to create the object.

See the QAxBaseWidget::control property documentation for details about supported patterns.

The interface returned in ptr must be referenced exactly once when this function returns. The interface provided by e.g. CoCreateInstance is already referenced, and there is no need to reference it again.

### `[protected]` bool QAxBase::initializeActive(IUnknown **ptr)

Connects to an active instance running on the current machine, and returns the IUnknown interface to the running object in ptr. This function returns true if successful, otherwise returns false.

This function is called by initialize() if the control string contains the substring "}&".

See also initialize().

### `[protected]` bool QAxBase::initializeFromFile(IUnknown **ptr)

Creates the COM object handling the filename in the control property, and returns the IUnknown interface to the object in ptr. This function returns true if successful, otherwise returns false.

This function is called by initialize() if the control string is the name of an existing file.

See also initialize().

### `[protected]` bool QAxBase::initializeLicensed(IUnknown **ptr)

Creates an instance of a licensed control, and returns the IUnknown interface to the object in ptr. This functions returns true if successful, otherwise returns false.

This function is called by initialize() if the control string contains the substring "}:". The license key needs to follow this substring.

See also initialize().

### `[protected]` bool QAxBase::initializeRemote(IUnknown **ptr)

Creates the instance on a remote server, and returns the IUnknown interface to the object in ptr. This function returns true if successful, otherwise returns false.

This function is called by initialize() if the control string contains the substring "/{". The information about the remote machine needs to be provided in front of the substring.

See also initialize().

### bool QAxBase::isNull() const

Returns true if there is no COM object loaded by this wrapper; otherwise return false.

See also control().

### QAxBase::PropertyBag QAxBase::propertyBag() const

Returns a name:value map of all the properties exposed by the COM object.

This is more efficient than getting multiple properties individually if the COM object supports property bags.

Warning: It is not guaranteed that the property bag implementation of the COM object returns all properties, or that the properties returned are the same as those available through the IDispatch interface.

See also setPropertyBag().

### `[virtual]` bool QAxBase::propertyWritable(const char *prop) const

Returns true if the property prop is writable; otherwise returns false. By default, all properties are writable.

Warning: Depending on the control implementation this setting might be ignored for some properties.

See also setPropertyWritable(), QAxBaseWidget::propertyChanged(), and QAxBaseObject::propertyChanged().

### long QAxBase::queryInterface(const QUuid &uuid, void **iface) const

Requests the interface uuid from the COM object and sets the value of iface to the provided interface, or to 0 if the requested interface could not be provided.

Returns the result of the QueryInterface implementation of the COM object.

See also control().

### QAxObject *QAxBase::querySubObject(const char *name, const QVariant &var1 = QVariant(), const QVariant &var2 = QVariant(), const QVariant &var3 = QVariant(), const QVariant &var4 = QVariant(), const QVariant &var5 = QVariant(), const QVariant &var6 = QVariant(), const QVariant &var7 = QVariant(), const QVariant &var8 = QVariant())

Returns a pointer to a QAxObject wrapping the COM object provided by the method or property name, passing passing the parameters var1, var1, var2, var3, var4, var5, var6, var7 and var8.

If name is provided by a method the string must include the full function prototype.

If name is a property the string must be the name of the property, and var1, ... var8 are ignored.

The returned QAxObject is a child of this object (which is either of type QAxObject or QAxWidget), and is deleted when this object is deleted. It is however safe to delete the returned object yourself, and you should do so when you iterate over lists of subobjects.

COM enabled applications usually have an object model publishing certain elements of the application as dispatch interfaces. Use this method to navigate the hierarchy of the object model, e.g.

     QAxWidget outlook("Outlook.Application");
     QAxObject *session = outlook.querySubObject("Session");
     if (session) {
         QAxObject *defFolder = session->querySubObject(
                                 "GetDefaultFolder(OlDefaultFolders)",
                                 "olFolderContacts");
         //...
     }

### QAxObject *QAxBase::querySubObject(const char *name, QList<QVariant> &vars)

The QVariant objects in vars are updated when the method has out-parameters.

This is an overloaded function.

### void QAxBase::setClassContext(ulong classContext)

Sets the context the ActiveX control will run in to classContext

Affects the "dwClsContext" argument when calling CoCreateInstance. This can be used to control in-proc vs. out-of-proc startup for controls supporting both alternatives. Also, it can be used to modify/reduce control permissions when used with CLSCTX_ENABLE_CLOAKING and an impersonation token.

Note that this function must be called before setControl() to have any effect.

See also classContext().

### void QAxBase::setPropertyBag(const QAxBase::PropertyBag &bag)

Sets the properties of the COM object to the corresponding values in bag.

Warning: You should only set property bags that have been returned by the propertyBag function, as it cannot be guaranteed that the property bag implementation of the COM object supports the same properties that are available through the IDispatch interface.

See also propertyBag().

### `[virtual]` void QAxBase::setPropertyWritable(const char *prop, bool ok)

Sets the property prop to writable if ok is true, otherwise sets prop to be read-only. By default, all properties are writable.

Warning: Depending on the control implementation this setting might be ignored for some properties.

See also propertyWritable(), QAxBaseWidget::propertyChanged(), and QAxBaseObject::propertyChanged().

### QStringList QAxBase::verbs() const

Returns the list of verbs that the COM object can execute. If the object does not implement IOleObject, or does not support any verbs, then this function returns an empty stringlist.

Note that the OLE default verbs (OLEIVERB_SHOW etc) are not included in the list.