QStateMachine class provides a hierarchical finite state machine. More...

Inheritance diagram for QStateMachine:

Classes
class	SignalEvent
	Signal event More...

class	WrappedEvent
	Inherits QEvent and holds a clone of an event associated with a QObject More...

Public Types
enum	Error

enum	EventPriority

Public Types inherited from QState
enum	ChildMode

enum	RestorePolicy

Public Signals
void	runningChanged (bool running)

void	started ()

void	stopped ()

Public Signals inherited from QState
void	childModeChanged ()

void	errorStateChanged ()

void	finished ()

void	initialStateChanged ()

void	propertiesAssigned ()

Public Signals inherited from QAbstractState
void	activeChanged (bool active)

void	entered ()

void	exited ()

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

void	objectNameChanged (const QString &objectName)

Public Slots
void	setRunning (bool running)

void	start ()

void	stop ()

Public Slots inherited from QObject
void	deleteLater ()

Public Methods
	QStateMachine (QObject *parent=nullptr)

	~QStateMachine ()

void	addDefaultAnimation (QAbstractAnimation *animation)

void	addState (QAbstractState *state)

bool	cancelDelayedEvent (int id)

void	clearError ()

QSet< QAbstractState * >	configuration () const

QList< QAbstractAnimation * >	defaultAnimations () const

Error	error () const

QString	errorString () const

bool	eventFilter (QObject watched, QEvent event) override

QState::RestorePolicy	globalRestorePolicy () const

bool	isAnimated () const

bool	isRunning () const

int	postDelayedEvent (QEvent *event, int delay)

void	postEvent (QEvent *event, EventPriority priority=NormalPriority)

void	removeDefaultAnimation (QAbstractAnimation *animation)

void	removeState (QAbstractState *state)

void	setAnimated (bool enabled)

void	setGlobalRestorePolicy (QState::RestorePolicy restorePolicy)

Public Methods inherited from QState
	QState (ChildMode childMode, QState *parent=nullptr)

	QState (QState *parent=nullptr)

	~QState ()

QAbstractTransition *	addTransition (QAbstractState *target)

void	addTransition (QAbstractTransition *transition)

template<class SignalClass , class... SignalArgs>
QSignalTransition *	addTransition (QObject sender, void (SignalClass::signal)(SignalArgs...), QAbstractState *target)

void	assignProperty (QObject *object, const QString &name, const QVariant &value)

ChildMode	childMode () const

QAbstractState *	errorState () const

QAbstractState *	initialState () const

void	removeTransition (QAbstractTransition *transition)

void	setChildMode (ChildMode mode)

void	setErrorState (QAbstractState *state)

void	setInitialState (QAbstractState *state)

QList< QAbstractTransition * >	transitions () const

Public Methods inherited from QAbstractState
	~QAbstractState ()

bool	active () const

QStateMachine *	machine () const

QState *	parentState () const

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

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

Protected Methods
bool	event (QEvent *event) override

void	onEntry (QEvent *event) override

void	onExit (QEvent *event) override

Protected Methods inherited from QAbstractState
	QAbstractState (QState *parent=nullptr)

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

virtual void	connectNotify (const QMetaMethod &signalMethod) const

virtual void	customEvent (QEvent *event)

virtual void	disconnectNotify (const QMetaMethod &signalMethod) const

bool	isSignalConnected (const QMetaMethod &signalMethod) const

int	receivers (const QString &signal) const

QObject *	sender () const

int	senderSignalIndex () const

virtual void	timerEvent (QTimerEvent *event)

Properties
	animated

	errorString

	globalRestorePolicy

	running

Properties inherited from QState
	childMode

	errorState

	initialState

Properties inherited from QAbstractState
	active

Properties inherited from QObject
	objectName

Additional Inherited Members
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 >())

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

	QObjectList

Detailed Description

The QStateMachine class provides a hierarchical finite state machine. This class is based on the concepts and notation of "Statecharts: A visual formalism for complex systems".

A state machine manages a set of states (classes that inherit from QAbstractState) and transitions (descendants of QAbstractTransition) between those states; these states and transitions define a state graph. Once a state graph has been built, the state machine can execute it. QStateMachine's execution algorithm is based on the "State Chart XML: State Machine Notation for Control Abstraction" algorithm. The State Machine gives several state graphs and the code to build them.

Use the addState() function to add a top-level state to the state machine. States are removed with the removeState() function. Removing states while the machine is running is discouraged.

Before the machine can be started, the initial state must be set. The initial state is the state that the machine enters when started. You can then start() the state machine. The started() signal is emitted when the initial state is entered.

The machine is event driven and keeps its own event loop. Events are posted to the machine through postEvent(). Note that this means that it executes asynchronously, and that it will not progress without a running event loop. You will normally not have to post events to the machine directly as the CopperSpice transitions, e.g., QEventTransition and its subclasses, handle this. But for custom transitions triggered by events, postEvent() is useful.

The state machine processes events and takes transitions until a top-level final state is entered; the state machine then emits the finished() signal. You can also stop() the state machine explicitly. The stopped() signal is emitted in this case.

The following code shows a state machine that will finish when a button is clicked:

QPushButton button;
 
QStateMachine machine;
QState *s1 = new QState();
s1->assignProperty(&button, "text", "Click me");
 
QFinalState *s2 = new QFinalState();
s1->addTransition(&button, SIGNAL(clicked()), s2);
 
machine.addState(s1);
machine.addState(s2);
machine.setInitialState(s1);
machine.start();

This code example uses QState, which inherits QAbstractState. The QState class provides a state that you can use to set properties and invoke methods on QObjects when the state is entered or exited. It also contains convenience functions for adding transitions, e.g., QSignalTransitions as in this example. See the QState class description for further details.

If an error is encountered, the machine will look for an error state, and if one is available, it will enter this state. The types of errors possible are described by the Error enum. After the error state is entered, the type of the error can be retrieved with error(). The execution of the state graph will not stop when the error state is entered. If no error state applies to the erroneous state, the machine will stop executing and an error message will be printed to the console.

See also: QAbstractState, QAbstractTransition, QState, State Machine

Member Enumeration Documentation

enum QStateMachine::Error

This enum type defines errors that can occur in the state machine at run time. When the state machine encounters an unrecoverable error at run time, it will set the error code returned by error(), the error message returned by errorString(), and enter an error state based on the context of the error.

Constant	Value	Description
`QStateMachine::NoError`	`0`	No error has occurred.
`QStateMachine::NoInitialStateError`	`1`	The machine has entered a QState with children which does not have an initial state set. The context of this error is the state which is missing an initial state.
`QStateMachine::NoDefaultStateInHistoryStateError`	`2`	The machine has entered a QHistoryState which does not have a default state set. The context of this error is the QHistoryState which is missing a default state.
`QStateMachine::NoCommonAncestorForTransitionError`	`3`	The machine has selected a transition whose source and targets are not part of the same tree of states, and thus are not part of the same state machine. Commonly, this could mean that one of the states has not been given any parent or added to any machine. The context of this error is the source state of the transition.

See also: setErrorState()

enum QStateMachine::EventPriority

This enum type specifies the priority of an event posted to the state machine using postEvent(). Events of high priority are processed before events of normal priority.

Constant	Value	Description
`QStateMachine::NormalPriority`	`0`	The event has normal priority.
`QStateMachine::HighPriority`	`1`	The event has high priority.

Constructor & Destructor Documentation

QStateMachine::QStateMachine ( QObject * parent = nullptr )

explicit

Constructs a new state machine with the given parent.

QStateMachine::~QStateMachine ( )

Destroys this state machine.

Method Documentation

void QStateMachine::addDefaultAnimation ( QAbstractAnimation * animation )

Adds a default animation to be considered for any transition.

void QStateMachine::addState ( QAbstractState * state )

Adds the given state to this state machine. The state becomes a top-level state.

If the state is already in a different machine, it will first be removed from its old machine, and then added to this machine.

See also: removeState(), setInitialState()

bool QStateMachine::cancelDelayedEvent ( int id )

Cancels the delayed event identified by the given id. The id should be a value returned by a call to postDelayedEvent(). Returns true if the event was successfully canceled, otherwise returns false.

Note: This method is thread-safe.

See also: postDelayedEvent()

void QStateMachine::clearError ( )

Clears the error string and error code of the state machine.

QSet< QAbstractState * > QStateMachine::configuration ( ) const

Returns the complete set of states that this state machine is currently in. If a state s is in this set then its parent is also in the set.

QList< QAbstractAnimation * > QStateMachine::defaultAnimations ( ) const

Returns the list of default animations that will be considered for any transition.

Error QStateMachine::error ( ) const

Returns the error code of the last error that occurred in the state machine.

QString QStateMachine::errorString ( ) const

Returns the value of the property errorString which contains the last error that occurred in the state machine.

bool QStateMachine::event ( QEvent * event )

overrideprotectedvirtual

Reimplemented from QState::event()

bool QStateMachine::eventFilter	(	QObject *	watched,
		QEvent *	event
	)

overridevirtual

Reimplemented from QObject::eventFilter()

QState::RestorePolicy QStateMachine::globalRestorePolicy ( ) const

Returns the restore policy of the state machine.

See also: setGlobalRestorePolicy()

bool QStateMachine::isAnimated ( ) const

Returns the value of the property animations which indicates whether animations are enabled for this state machine.

bool QStateMachine::isRunning ( ) const

Returns whether this state machine is running.

See also: start(), stop()

void QStateMachine::onEntry ( QEvent * event )

overrideprotectedvirtual

This method will call start() to start the state machine.

Reimplemented from QState::onEntry()

void QStateMachine::onExit ( QEvent * event )

overrideprotectedvirtual

This method will call stop() to stop the state machine and subsequently emit the stopped() signal.

Reimplemented from QState::onExit()

int QStateMachine::postDelayedEvent	(	QEvent *	event,
		int	delay
	)

Posts the given event for processing by this state machine, with the given delay in milliseconds. Returns an identifier associated with the delayed event, or -1 if the event could not be posted.

This method returns immediately. When the delay has expired, the event will be added to the state machine's event queue for processing. The state machine takes ownership of the event and deletes it once it has been processed.

You can only post events when the state machine is running.

Note: This method is thread-safe.

See also: cancelDelayedEvent(), postEvent()

void QStateMachine::postEvent	(	QEvent *	event,
		EventPriority	priority = `NormalPriority`
	)

Posts the given event of the given priority for processing by this state machine.

This method returns immediately. The event is added to the state machine's event queue. Events are processed in the order posted. The state machine takes ownership of the event and deletes it once it has been processed.

You can only post events when the state machine is running.

Note: This method is thread-safe.

See also: postDelayedEvent()

void QStateMachine::removeDefaultAnimation ( QAbstractAnimation * animation )

Removes animation from the list of default animations.

void QStateMachine::removeState ( QAbstractState * state )

Removes the given state from this state machine. The state machine releases ownership of the state.

See also: addState()

void QStateMachine::runningChanged ( bool running )

signal

This signal is emitted when the running property is changed with running as argument.

See also: QStateMachine::running

void QStateMachine::setAnimated ( bool enabled )

Sets the value of the property animations to the given enabled. Indicates whether animations are enabled for this state machine.

void QStateMachine::setGlobalRestorePolicy ( QState::RestorePolicy restorePolicy )

Sets the restore policy of the state machine to restorePolicy. The default restore policy is QState::DontRestoreProperties.

See also: globalRestorePolicy()

void QStateMachine::setRunning ( bool running )

slot

Sets the running property to the value of running.

See also: QStateMachine::running

void QStateMachine::start ( )

slot

Starts this state machine. The machine will reset its configuration and transition to the initial state. When a final top-level state (QFinalState) is entered, the machine will emit the finished() signal.

Note: A state machine will not run without a running event loop, such as the main application event loop started with QCoreApplication::exec() or QApplication::exec().

See also: started(), finished(), stop(), initialState()

void QStateMachine::started ( )

signal

This signal is emitted when the state machine has entered its initial state (QStateMachine::initialState).

See also: QStateMachine::finished(), QStateMachine::start()

void QStateMachine::stop ( )

slot

Stops this state machine. The state machine will stop processing events and then emit the stopped() signal.

See also: stopped(), start()

void QStateMachine::stopped ( )

signal

This signal is emitted when the state machine has stopped.

See also: QStateMachine::stop(), QStateMachine::finished()

Property Documentation

QStateMachine::animated

This property holds whether animations are enabled. The default value of this property is true.

See also: QAbstractTransition::addAnimation()

Properties	Class Methods
read	isAnimated
write	setAnimated

QStateMachine::errorString

This property holds the error string of this state machine.

Properties	Class Methods
read	errorString

QStateMachine::globalRestorePolicy

This property holds the restore policy for states of this state machine. The default value of this property is QState::DontRestoreProperties.

Properties	Class Methods
read	globalRestorePolicy
write	setGlobalRestorePolicy

QStateMachine::running

This property holds the running state of this state machine.

Properties	Class Methods
read	isRunning
write	setRunning
notify	runningChanged

Classes

Public Types

Public Signals

Public Slots

Public Methods

Protected Methods

Properties

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Property Documentation