- Qt 6.9
- Qt D-Bus
- C++ Classes
- QDBusAbstractInterface
- Qt 6.9.3 Reference Documentation

# QDBusAbstractInterface Class

The QDBusAbstractInterface class is the base class for all D-Bus interfaces in the Qt D-Bus binding, allowing access to remote interfaces. More...

Header: | `#include <QDBusAbstractInterface>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS DBus)` `target_link_libraries(mytarget PRIVATE Qt6::DBus)`
qmake: | `QT += dbus`
Inherits: | QObject
Inherited By: | QDBusConnectionInterface and QDBusInterface

- List of all members, including inherited members

## Public Functions

virtual | ~QDBusAbstractInterface()
QDBusPendingCall | asyncCall(const QString &method, Args &&... args)
QDBusPendingCall | asyncCallWithArgumentList(const QString &method, const QList<QVariant> &args)
QDBusMessage | call(const QString &method, Args &&... args)
QDBusMessage | call(QDBus::CallMode mode, const QString &method, Args &&... args)
QDBusMessage | callWithArgumentList(QDBus::CallMode mode, const QString &method, const QList<QVariant> &args)
bool | callWithCallback(const QString &method, const QList<QVariant> &args, QObject *receiver, const char *returnMethod, const char *errorMethod)
bool | callWithCallback(const QString &method, const QList<QVariant> &args, QObject *receiver, const char *slot)
QDBusConnection | connection() const
QString | interface() const
`(since 6.7)` bool | isInteractiveAuthorizationAllowed() const
bool | isValid() const
QDBusError | lastError() const
QString | path() const
QString | service() const
`(since 6.7)` void | setInteractiveAuthorizationAllowed(bool enable)
void | setTimeout(int timeout)
int | timeout() const

## Detailed Description

Generated-code classes also derive from QDBusAbstractInterface, all methods described here are also valid for generated-code classes. In addition to those described here, generated-code classes provide member functions for the remote methods, which allow for compile-time checking of the correct parameters and return values, as well as property type-matching and signal parameter-matching.

See also The QDBus compiler and QDBusInterface.

## Member Function Documentation

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

Releases this object's resources.

### template <typename... Args> QDBusPendingCall QDBusAbstractInterface::asyncCall(const QString &method, Args &&... args)

Calls the method method on this interface and passes args to the method. All args must be convertible to QVariant.

The parameters to `call` are passed on to the remote function via D-Bus as input arguments. The returned QDBusPendingCall object can be used to find out information about the reply.

It can be used the following way:

     QDBusPendingCall pcall = interface->asyncCall("GetAPIVersion"_L1);
     auto watcher = new QDBusPendingCallWatcher(pcall, this);

     QObject::connect(watcher, &QDBusPendingCallWatcher::finished, this,
                      [&](QDBusPendingCallWatcher *w) {
         QString value = retrieveValue();
         QDBusPendingReply<int> reply(*w);
         QDBusPendingCall pcall;
         if (reply.argumentAt<0>() >= 14)
             pcall = interface->asyncCall("ProcessWorkUnicode"_L1, value);
         else
             pcall = interface->asyncCall("ProcessWork"_L1, "UTF-8"_L1, value.toUtf8());

         w = new QDBusPendingCallWatcher(pcall);
         QObject::connect(w,  &QDBusPendingCallWatcher::finished, this,
                          &Abstract_DBus_Interface::callFinishedSlot);
     });

This example illustrates function calling with 0, 1 and 2 parameters and illustrates different parameter types passed in each (the first call to `"ProcessWorkUnicode"` will contain one Unicode string, the second call to `"ProcessWork"` will contain one string and one byte array). See call() for the same example in blocking (synchronous) calls.

Note: Before Qt 5.14, this function accepted a maximum of just eight (8) arguments.

Note: Method calls to local `QDBusServer`'s are never asynchronous due to implementation limitations.

See also asyncCallWithArgumentList().

### QDBusPendingCall QDBusAbstractInterface::asyncCallWithArgumentList(const QString &method, const QList<QVariant> &args)

Places a call to the remote method specified by method on this interface, using args as arguments. This function returns a QDBusPendingCall object that can be used to track the status of the reply and access its contents once it has arrived.

Normally, you should place calls using asyncCall().

Note: Method calls to objects registered by the application itself are never asynchronous due to implementation limitations.

Note: This function is thread-safe.

### template <typename... Args> QDBusMessage QDBusAbstractInterface::call(const QString &method, Args &&... args)

Calls the method method on this interface and passes args to the method. All args must be convertible to QVariant.

The parameters to `call` are passed on to the remote function via D-Bus as input arguments. Output arguments are returned in the QDBusMessage reply. If the reply is an error reply, lastError() will also be set to the contents of the error message.

It can be used the following way:

     QString value = retrieveValue();
     QDBusMessage reply;

     QDBusReply<int> api = interface->call("GetAPIVersion"_L1);
     if (api >= 14)
       reply = interface->call("ProcessWorkUnicode"_L1, value);
     else
       reply = interface->call("ProcessWork"_L1, "UTF-8"_L1, value.toUtf8());

This example illustrates function calling with 0, 1 and 2 parameters and illustrates different parameter types passed in each (the first call to `"ProcessWorkUnicode"` will contain one Unicode string, the second call to `"ProcessWork"` will contain one string and one byte array). See asyncCall() for the same example in non-blocking (asynchronous) calls.

Note: Before Qt 5.14, this function accepted a maximum of just eight (8) arguments.

See also callWithArgumentList().

### template <typename... Args> QDBusMessage QDBusAbstractInterface::call(QDBus::CallMode mode, const QString &method, Args &&... args)

Calls the method method on this interface and passes args to the method. All args must be convertible to QVariant.

If mode is `NoWaitForReply`, then this function will return immediately after placing the call, without waiting for a reply from the remote method. Otherwise, mode indicates whether this function should activate the Qt Event Loop while waiting for the reply to arrive.

If this function reenters the Qt event loop in order to wait for the reply, it will exclude user input. During the wait, it may deliver signals and other method calls to your application. Therefore, it must be prepared to handle a reentrancy whenever a call is placed with call().

Note: Before Qt 5.14, this function accepted a maximum of just eight (8) arguments.

This is an overloaded function.

See also callWithArgumentList().

### QDBusMessage QDBusAbstractInterface::callWithArgumentList(QDBus::CallMode mode, const QString &method, const QList<QVariant> &args)

Places a call to the remote method specified by method on this interface, using args as arguments. This function returns the message that was received as a reply, which can be a normal QDBusMessage::ReplyMessage (indicating success) or QDBusMessage::ErrorMessage (if the call failed). The mode parameter specifies how this call should be placed.

If the call succeeds, lastError() will be cleared; otherwise, it will contain the error this call produced.

Normally, you should place calls using call().

Warning: If you use `UseEventLoop`, your code must be prepared to deal with any reentrancy: other method calls and signals may be delivered before this function returns, as well as other Qt queued signals and events.

Note: This function is thread-safe.

### bool QDBusAbstractInterface::callWithCallback(const QString &method, const QList<QVariant> &args, QObject *receiver, const char *returnMethod, const char *errorMethod)

Places a call to the remote method specified by method on this interface, using args as arguments. This function returns immediately after queueing the call. The reply from the remote function is delivered to the returnMethod on object receiver. If an error occurs, the errorMethod on object receiver is called instead.

This function returns `true` if the queueing succeeds. It does not indicate that the executed call succeeded. If it fails, the errorMethod is called. If the queueing failed, this function returns `false` and no slot will be called.

The returnMethod must have as its parameters the types returned by the function call. Optionally, it may have a QDBusMessage parameter as its last or only parameter. The errorMethod must have a QDBusError as its only parameter.

Note: Method calls to objects registered by the application itself are never asynchronous due to implementation limitations.

See also QDBusError and QDBusMessage.

### bool QDBusAbstractInterface::callWithCallback(const QString &method, const QList<QVariant> &args, QObject *receiver, const char *slot)

This function is deprecated. Please use the overloaded version.

Places a call to the remote method specified by method on this interface, using args as arguments. This function returns immediately after queueing the call. The reply from the remote function or any errors emitted by it are delivered to the slot slot on object receiver.

This function returns `true` if the queueing succeeded: it does not indicate that the call succeeded. If it failed, the slot will be called with an error message. lastError() will not be set under those circumstances.

This is an overloaded function.

See also QDBusError and QDBusMessage.

### QDBusConnection QDBusAbstractInterface::connection() const

Returns the connection this interface is associated with.

### QString QDBusAbstractInterface::interface() const

Returns the name of this interface.

### `[since 6.7]` bool QDBusAbstractInterface::isInteractiveAuthorizationAllowed() const

Returns whether, for asynchronous calls, the caller is prepared to wait for interactive authorization.

The default is `false`.

This function was introduced in Qt 6.7.

See also setInteractiveAuthorizationAllowed() and QDBusMessage::setInteractiveAuthorizationAllowed().

### bool QDBusAbstractInterface::isValid() const

Returns `true` if this is a valid reference to a remote object. It returns `false` if there was an error during the creation of this interface (for instance, if the remote application does not exist).

Note: when dealing with remote objects, it is not always possible to determine if it exists when creating a QDBusInterface.

### QDBusError QDBusAbstractInterface::lastError() const

Returns the error the last operation produced, or an invalid error if the last operation did not produce an error.

### QString QDBusAbstractInterface::path() const

Returns the object path that this interface is associated with.

### QString QDBusAbstractInterface::service() const

Returns the name of the service this interface is associated with.

### `[since 6.7]` void QDBusAbstractInterface::setInteractiveAuthorizationAllowed(bool enable)

Configures whether, for asynchronous calls, the caller is prepared to wait for interactive authorization.

If enable is set to `true`, the D-Bus messages generated for asynchronous calls via this interface will set the `ALLOW_INTERACTIVE_AUTHORIZATION` flag.

This flag is only useful when unprivileged code calls a more privileged method call, and an authorization framework is deployed that allows possibly interactive authorization.

The default is `false`.

This function was introduced in Qt 6.7.

See also isInteractiveAuthorizationAllowed() and QDBusMessage::setInteractiveAuthorizationAllowed().

### void QDBusAbstractInterface::setTimeout(int timeout)

Sets the timeout in milliseconds for all future DBus calls to timeout. -1 means the default DBus timeout (usually 25 seconds).

See also timeout().

### int QDBusAbstractInterface::timeout() const

Returns the current value of the timeout in milliseconds. -1 means the default DBus timeout (usually 25 seconds).

See also setTimeout().