QAbstractState Class | Qt State Machine | Qt 6.12.0
Description: The QAbstractState class is the base class of states of a QStateMachine.
Keywords: class

- Qt 6.12
- Qt State Machine
- C++ Classes
- QAbstractState
- Qt 6.12.0 Reference Documentation

# QAbstractState Class

The QAbstractState class is the base class of states of a QStateMachine. More...

Header: | `#include <QAbstractState>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS StateMachine)` `target_link_libraries(mytarget PRIVATE Qt6::StateMachine)`
qmake: | `QT += statemachine`
Inherits: | QObject
Inherited By: | QFinalState, QHistoryState, and QState

- List of all members, including inherited members

## Properties

- active : bool

## Public Functions

virtual | ~QAbstractState()
bool | active() const
QBindable<bool> | bindableActive()
QStateMachine * | machine() const
QState * | parentState() const

## Signals

void | activeChanged(bool active)
void | entered()
void | exited()

## Protected Functions

| QAbstractState(QState *parent = nullptr)
virtual void | onEntry(QEvent *event) = 0
virtual void | onExit(QEvent *event) = 0

## Reimplemented Protected Functions

virtual bool | event(QEvent *e) override

## Detailed Description

The QAbstractState class is the abstract base class of states that are part of a QStateMachine. It defines the interface that all state objects have in common. QAbstractState is part of Qt State Machine Framework.

The entered() signal is emitted when the state has been entered. The exited() signal is emitted when the state has been exited.

The parentState() function returns the state's parent state. The machine() function returns the state machine that the state is part of.

### Subclassing

The onEntry() function is called when the state is entered; reimplement this function to perform custom processing when the state is entered.

The onExit() function is called when the state is exited; reimplement this function to perform custom processing when the state is exited.

## Property Documentation

### `[bindable read-only]` active : bool

Note: This property supports QProperty bindings.

This property holds the active property of this state. A state is active between entered() and exited() signals.

Access functions:

bool | active() const

Notifier signal:

void | activeChanged(bool active)

## Member Function Documentation

### `[protected]` QAbstractState::QAbstractState(QState *parent = nullptr)

Constructs a new state with the given parent state.

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

Destroys this state.

### bool QAbstractState::active() const

Returns whether this state is active.

Note: Getter function for property active.

See also activeChanged(bool), entered(), and exited().

### `[signal]` void QAbstractState::activeChanged(bool active)

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

Note: Notifier signal for property active.

See also QAbstractState::active, entered(), and exited().

### `[private signal]` void QAbstractState::entered()

This signal is emitted when the state has been entered (after onEntry() has been called).

Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.

### `[override virtual protected]` bool QAbstractState::event(QEvent *e)

Reimplements: QObject::event(QEvent *e).

### `[private signal]` void QAbstractState::exited()

This signal is emitted when the state has been exited (after onExit() has been called).

Note: This is a private signal. It can be used in signal connections but cannot be emitted by the user.

### QStateMachine *QAbstractState::machine() const

Returns the state machine that this state is part of, or `nullptr` if the state is not part of a state machine.

### `[pure virtual protected]` void QAbstractState::onEntry(QEvent *event)

This function is called when the state is entered. The given event is what caused the state to be entered. Reimplement this function to perform custom processing when the state is entered.

### `[pure virtual protected]` void QAbstractState::onExit(QEvent *event)

This function is called when the state is exited. The given event is what caused the state to be exited. Reimplement this function to perform custom processing when the state is exited.

### QState *QAbstractState::parentState() const

Returns this state's parent state, or `nullptr` if the state has no parent state.