The QFutureWatcher class allows monitoring a QFuture using signals and slots. More...

Inheritance diagram for QFutureWatcher< T >:

Public Methods
	QFutureWatcher (QObject *parent=nullptr)

	~QFutureWatcher ()

QFuture< T >	future () const

T	result () const

T	resultAt (int index) const

void	setFuture (const QFuture< T > &future)

Public Methods inherited from QFutureWatcherBase
bool	event (QEvent *event) override

bool	isCanceled () const

bool	isFinished () const

bool	isPaused () const

bool	isRunning () const

bool	isStarted () const

int	progressMaximum () const

int	progressMinimum () const

QString	progressText () const

int	progressValue () const

void	setPendingResultsLimit (int limit)

void	waitForFinished ()

Public Methods inherited from QObject
	QObject (QObject *parent=nullptr)

	~QObject ()

bool	blockSignals (bool block)

const QList< QObject * > &	children () const

bool	connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

bool	disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

bool	disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const

void	dumpObjectInfo ()

void	dumpObjectTree ()

QList< QString >	dynamicPropertyNames () const

virtual bool	eventFilter (QObject watched, QEvent event)

template<typename T >
T	findChild (const QString &childName=QString ()) const

template<class T >
QList< T >	findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

template<class T >
QList< T >	findChildren (const QString &childName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const

bool	inherits (const QString &className) const

void	installEventFilter (QObject *filterObj)

bool	isWidgetType () const

bool	isWindowType () const

void	killTimer (int id)

const QMetaObject *	metaObject () const

void	moveToThread (QThread *targetThread)

QString	objectName () const

QObject *	parent () const

template<class T = QVariant>
T	property (const QString &name) const

void	removeEventFilter (QObject *obj)

void	setObjectName (const QString &name)

void	setParent (QObject *parent)

bool	setProperty (const QString &name, const QVariant &value)

bool	signalsBlocked () const

int	startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)

QThread *	thread () const

Additional Inherited Members
Public Signals inherited from QFutureWatcherBase
void	canceled ()

void	finished ()

void	paused ()

void	progressRangeChanged (int minimum, int maximum)

void	progressTextChanged (const QString &progressText)

void	progressValueChanged (int progressValue)

void	resultReadyAt (int index)

void	resultsReadyAt (int beginIndex, int endIndex)

void	resumed ()

void	started ()

Public Signals inherited from QObject
void	destroyed (QObject *obj=nullptr)

void	objectNameChanged (const QString &objectName)

Public Slots inherited from QFutureWatcherBase
void	cancel ()

void	pause ()

void	resume ()

void	setPaused (bool paused)

void	togglePaused ()

Public Slots inherited from QObject
void	deleteLater ()

Static Public Methods inherited from QObject
static bool	connect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

static bool	connect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())

static bool	connect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	connect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)

static bool	disconnect (const QObject sender, const QMetaMethod &signalMethod, const QObject receiver, const QMetaMethod &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, const QString &signalMethod, const QString &location, const QObject receiver, const QString &slotMethod)

static bool	disconnect (const QObject sender, std::nullptr_t, const QObject receiver, std::nullptr_t)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver receiver, SlotReturn (SlotClass::slotMethod)(SlotArgs...))

template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)

template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool	disconnect (const Sender sender, void (SignalClass::signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)

static QMetaObject &	staticMetaObject ()

static QString	tr (const char text, const char comment=nullptr, std::optional< int > numArg=std::optional< int >())

Protected Methods inherited from QFutureWatcherBase
void	connectNotify (const QMetaMethod &signal) const override

void	disconnectNotify (const QMetaMethod &signal) const override

Protected Methods inherited from QObject
virtual void	childEvent (QChildEvent *event)

virtual void	customEvent (QEvent *event)

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Properties inherited from QObject
	objectName

Related Functions inherited from QObject
T	qobject_cast (QObject *object)

	QObjectList

Detailed Description

template<typename T>
class QFutureWatcher< T >

The QFutureWatcher class allows monitoring a QFuture using signals and slots. QFutureWatcher provides information and notifications about a QFuture. Use the setFuture() function to start watching a particular QFuture. The future() function returns the future set with setFuture().

For convenience, several of QFuture's functions are also available in QFutureWatcher: progressValue(), progressMinimum(), progressMaximum(), progressText(), isStarted(), isFinished(), isRunning(), isCanceled(), isPaused(), waitForFinished(), result(), and resultAt(). The cancel(), setPaused(), pause(), resume(), and togglePaused() functions are slots in QFutureWatcher.

Status changes are reported via the started(), finished(), canceled(), paused(), resumed(), resultReadyAt(), and resultsReadyAt() signals. Progress information is provided from the progressRangeChanged(), void progressValueChanged(), and progressTextChanged() signals.

Throttling control is provided by the setPendingResultsLimit() function. When the number of pending resultReadyAt() or resultsReadyAt() signals exceeds the limit, the computation represented by the future will be throttled automatically. The computation will resume once the number of pending signals drops below the limit.

The following example shows starting a computation and getting a slot callback when it is finished.

// Instantiate the objects and connect to the finished signal.
MyClass myObject;
QFutureWatcher<int> watcher;
connect(&watcher, SIGNAL(finished()), &myObject, SLOT(handleFinished()));
 
// Start the computation.
QFuture<int> future = QtConcurrent::run(...);
watcher.setFuture(future);

Be aware that not all asynchronous computations can be canceled or paused. For example, the future returned by QtConcurrent::run() can not be canceled; but the future returned by QtConcurrent::mappedReduced() can.

QFutureWatcher<void> is specialized to not contain any of the result fetching functions. Any QFuture<T> can be watched by a QFutureWatcher<void> as well. This is useful if only status or progress information is needed; not the actual result data.

See also: QFuture, Concurrent Programming

Constructor & Destructor Documentation

template<typename T >

QFutureWatcher< T >::QFutureWatcher ( QObject * parent = nullptr )

inline

Constructs a new QFutureWatcher with the given parent.

template<typename T >

QFutureWatcher< T >::~QFutureWatcher ( )

inline

Destroys the QFutureWatcher.

Method Documentation

template<typename T >

QFuture< T > QFutureWatcher< T >::future ( ) const

inline

Returns the watched future.

See also: setFuture()

template<typename T >

T QFutureWatcher< T >::result ( ) const

inline

Returns the first result in the future(). If the result is not immediately available, this function will block and wait for the result to become available. This is a convenience method for calling resultAt(0).

See also: resultAt()

template<typename T >

T QFutureWatcher< T >::resultAt ( int index ) const

inline

Returns the result at index in the future(). If the result is not immediately available, this function will block and wait for the result to become available.

See also: result()

template<typename T >

void QFutureWatcher< T >::setFuture ( const QFuture< T > & future )

inline

Starts watching the given future.

One of the signals might be emitted for the current state of the future. For example, if the future is already stopped, the finished signal will be emitted.

To avoid a race condition it is important to call this function after doing the connections.

See also: future()

Public Methods

Additional Inherited Members

Detailed Description

template<typename T> class QFutureWatcher< T >

Constructor & Destructor Documentation

Method Documentation

template<typename T>
class QFutureWatcher< T >