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Diffstat (limited to 'src')
| -rw-r--r-- | src/corelib/statemachine/qstatemachine.cpp | 140 |
1 files changed, 85 insertions, 55 deletions
diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp index c2b2696..2f620c7 100644 --- a/src/corelib/statemachine/qstatemachine.cpp +++ b/src/corelib/statemachine/qstatemachine.cpp @@ -83,68 +83,98 @@ QT_BEGIN_NAMESPACE \since 4.6 \ingroup statemachine - The QStateMachine class provides a hierarchical finite state machine based - on \l{Statecharts: A visual formalism for complex systems}{Statecharts} - concepts and notation. QStateMachine is part of \l{The State Machine - Framework}. - - A state machine manages a set of states (QAbstractState objects) and - transitions (QAbstractTransition objects) between those states; the states - and the transitions collectively define a state graph. Once a state graph - has been defined, the state machine can execute it. QStateMachine's - execution algorithm is based on the \l{State Chart XML: State Machine - Notation for Control Abstraction}{State Chart XML (SCXML)} algorithm. - - 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. This is + QStateMachine is based on the concepts and notation of + \l{Statecharts: A visual formalism for complex + systems}{Statecharts}. QStateMachine is part of \l{The State + Machine Framework}. + + 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. \l{QStateMachine}'s + execution algorithm is based on the \l{State Chart XML: State + Machine Notation for Control Abstraction}{State Chart XML (SCXML)} + algorithm. The framework's \l{The State Machine + Framework}{overview} gives several state graphs and the code to + build them. + + The rootState() is the parent of all top-level states in the + machine; it is used, for instance, when the state graph is + deleted. It is created by the machine. + + Use the addState() function to add a state to the state machine. + All top-level states are added to the root state. States are + removed with the removeState() function. Removing states while the + machine is running is discouraged. + + Before the machine can be started, the \l{initialState}{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 Qt's 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 snippet shows a state machine that will finish when a button + is clicked: + + \code + 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(); + \endcode + + 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 \l{QObject}s when the state is entered or + exited. It also contains convenience functions for adding + transitions, e.g., \l{QSignalTransition}s as in this example. See + the QState class description for further details. + + If an error is encountered, the machine will enter the + \l{errorState}{error state}, which is a special state created by + the machine. The types of errors possible are described by the + \l{QStateMachine::}{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. + So it is possible to handle the error, for instance, by connecting + to the \l{QAbstractState::}{entered()} signal of the error state. + It is also possible to set a custom error state with + setErrorState(). + + \omit This stuff will be moved elsewhere +This is typically used in conjunction with \l{Signals and Slots}{signals}; the signals determine the flow of the state graph, whereas the states' property assignments and method invocations are the actions. - Use the addState() function to add a state to the state machine; - alternatively, pass the machine's rootState() to the state constructor. Use - the removeState() function to remove a state from the state machine. - - The following snippet shows a state machine that will finish when a button - is clicked: - - \code - 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(); - \endcode - - The setInitialState() function sets the state machine's initial state; this - state is entered when the state machine is started. - - The start() function starts the state machine. The state machine executes - asynchronously, i.e. you need to run an event loop in order for it to make - progress. The started() signal is emitted when the state machine has entered - the initial state. - - The state machine processes events and takes transitions until a top-level - final state is entered; the state machine then emits the finished() signal. - - The stop() function stops the state machine. The stopped() signal is emitted - when the state machine has stopped. - The postEvent() function posts an event to the state machine. This is useful when you are using custom events to trigger transitions. + \endomit - The rootState() function returns the state machine's root state. All - top-level states have the root state as their parent. - - \sa QAbstractState, QAbstractTransition + \sa QAbstractState, QAbstractTransition, QState, {The State Machine Framework} */ /*! |