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QDBusPendingCallWatcher Class

The QDBusPendingCallWatcher class provides a convenient way for waiting for asynchronous replies. More...

Header: #include <QDBusPendingCallWatcher>
qmake: QT += dbus
Since: Qt 4.5
Inherits: QObject and QDBusPendingCall

Public Functions

QDBusPendingCallWatcher(const QDBusPendingCall &call, QObject *parent = nullptr)
virtual ~QDBusPendingCallWatcher()
bool isFinished() const
void waitForFinished()

Signals

void finished(QDBusPendingCallWatcher *self = nullptr)

Static Public Members

const QMetaObject staticMetaObject

Additional Inherited Members

  • 1 property inherited from QObject
  • 1 public slot inherited from QObject
  • 9 protected functions inherited from QObject

Detailed Description

The QDBusPendingCallWatcher class provides a convenient way for waiting for asynchronous replies.

The QDBusPendingCallWatcher provides the finished() signal that will be emitted when a reply arrives.

It is usually used like the following example:

    QDBusPendingCall async = iface->asyncCall("RemoteMethod", value1, value2);
    QDBusPendingCallWatcher *watcher = new QDBusPendingCallWatcher(async, this);

    QObject::connect(watcher, SIGNAL(finished(QDBusPendingCallWatcher*)),
                     this, SLOT(callFinishedSlot(QDBusPendingCallWatcher*)));

Note that it is not necessary to keep the original QDBusPendingCall object around since QDBusPendingCallWatcher inherits from that class too.

The slot connected to by the above code could be something similar to the following:

void MyClass::callFinishedSlot(QDBusPendingCallWatcher *call)
{
    QDBusPendingReply<QString, QByteArray> reply = *call;
    if (reply.isError()) {
        showError();
    } else {
        QString text = reply.argumentAt<0>();
        QByteArray data = reply.argumentAt<1>();
        showReply(text, data);
    }
    call->deleteLater();
}

Note the use of QDBusPendingReply to validate the argument types in the reply. If the reply did not contain exactly two arguments (one string and one QByteArray), QDBusPendingReply::isError() will return true.

See also QDBusPendingReply and QDBusAbstractInterface::asyncCall().

Member Function Documentation

QDBusPendingCallWatcher::QDBusPendingCallWatcher(const QDBusPendingCall &call, QObject *parent = nullptr)

Creates a QDBusPendingCallWatcher object to watch for replies on the asynchronous pending call call and sets this object's parent to parent.

[virtual] QDBusPendingCallWatcher::~QDBusPendingCallWatcher()

Destroys this object. If this QDBusPendingCallWatcher object was the last reference to the unfinished pending call, the call will be canceled.

[signal] void QDBusPendingCallWatcher::finished(QDBusPendingCallWatcher *self = nullptr)

This signal is emitted when the pending call has finished and its reply is available. The self parameter is a pointer to the object itself, passed for convenience so that the slot can access the properties and determine the contents of the reply.

bool QDBusPendingCallWatcher::isFinished() const

Returns true if the pending call has finished processing and the reply has been received.

Note that this function only changes state if you call waitForFinished() or if an external D-Bus event happens, which in general only happens if you return to the event loop execution.

See also QDBusPendingReply::isFinished().

void QDBusPendingCallWatcher::waitForFinished()

Suspends the execution of the calling thread until the reply is received and processed. After this function returns, isFinished() should return true, indicating the reply's contents are ready to be processed.

See also QDBusPendingReply::waitForFinished().

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