QScxmlCppDataModel Class

The QScxmlCppDataModel class is a C++ data model for a Qt SCXML state machine. 更多...

頭：	#include <QScxmlCppDataModel>
qmake:	QT += scxml
Since:	Qt 5.7
繼承：	QScxmlDataModel

該類在 Qt 5.7 引入。

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公共函數

	QScxmlCppDataModel (QObject * parent = nullptr)
bool	inState (const QString & stateName ) const
const QScxmlEvent &	scxmlEvent () const

重實現公共函數

virtual void	evaluateAssignment (QScxmlExecutableContent::EvaluatorId id , bool * ok ) override
virtual void	evaluateForeach (QScxmlExecutableContent::EvaluatorId id , bool * ok , QScxmlDataModel::ForeachLoopBody * body ) override
virtual void	evaluateInitialization (QScxmlExecutableContent::EvaluatorId id , bool * ok ) override
virtual bool	hasScxmlProperty (const QString & name ) const override
virtual QVariant	scxmlProperty (const QString & name ) const override
virtual void	setScxmlEvent (const QScxmlEvent & event ) override
virtual bool	setScxmlProperty (const QString & name , const QVariant & value , const QString & context ) override
virtual bool	setup (const QVariantMap & initialDataValues ) override

詳細描述

The C++ data model for SCXML lets you write C++ code for expr 屬性和 <script> 元素。 數據部分 of the data model is backed by a subclass of QScxmlCppDataModel, for which the Qt SCXML compiler ( qscxmlc ) will generate the dispatch methods. It cannot be used when loading an SCXML file at runtime.

Usage is through the datamodel 屬性在 <scxml> 元素：

<scxml datamodel="cplusplus:TheDataModel:thedatamodel.h"  ....>

The format of the datamodel attribute is: cplusplus:<class-name>:<classdef-header> . So, for the example above, there should be a file thedatamodel.h containing a subclass of QScxmlCppDataModel, containing at least the following:

#include "qscxmlcppdatamodel.h"
class TheDataModel: public QScxmlCppDataModel
{
    Q_OBJECT
    Q_SCXML_DATAMODEL
};

The Q_SCXML_DATAMODEL has to appear in the private section of the class definition, for example right after the opening bracket, or after a Q_OBJECT macro. This macro expands to the declaration of some virtual methods whose implementation is generated by the Qt SCXML compiler.

The Qt SCXML compiler will generate the various evaluateTo methods, and convert expressions and scripts into lambdas inside those methods. For example:

<scxml datamodel="cplusplus:TheDataModel:thedatamodel.h" xmlns="http://www.w3.org/2005/07/scxml" version="1.0" name="MediaPlayerStateMachine">
    <state id="stopped">
        <transition event="tap" cond="isValidMedia()" target="playing"/>
    </state>
    <state id="playing">
        <onentry>
            <script>
                media = eventData().value(QStringLiteral(&quot;media&quot;)).toString();
            </script>
            <send event="playbackStarted">
                <param name="media" expr="media"/>
            </send>
        </onentry>
    </state>
</scxml>

This will result in:

bool TheDataModel::evaluateToBool(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
    // ....
        return [this]()->bool{ return isValidMedia(); }();
    // ....
}
QVariant TheDataModel::evaluateToVariant(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
    // ....
        return [this]()->QVariant{ return media; }();
    // ....
}
void TheDataModel::evaluateToVoid(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
    // ....
        [this]()->void{ media = eventData().value(QStringLiteral("media")).toString(); }();
    // ....
}

So, you are not limited to call functions. In a <script> element you can put zero or more C++ statements, and in cond or expr attributes you can use any C++ expression that can be converted to the respective bool or QVariant . And, as the this pointer is also captured, you can call or access the data model (the media attribute in the example above). For the full example, see Qt SCXML: Media Player QML Example (C++ Data Model) .

另請參閱 QScxmlStateMachine and QScxmlDataModel .

成員函數文檔編製

QScxmlCppDataModel:: QScxmlCppDataModel ( QObject * parent = nullptr)

Creates a new C++ data model with the parent object parent .

`[override virtual]` void QScxmlCppDataModel:: evaluateAssignment ( QScxmlExecutableContent::EvaluatorId id , bool * ok )

重實現： QScxmlDataModel::evaluateAssignment (QScxmlExecutableContent::EvaluatorId id, bool *ok).

This method does not perform any action, ignores id , and sets ok to false . Override it in your specific data model in order to implement <assign> .

`[override virtual]` void QScxmlCppDataModel:: evaluateForeach ( QScxmlExecutableContent::EvaluatorId id , bool * ok , QScxmlDataModel::ForeachLoopBody * body )

重實現： QScxmlDataModel::evaluateForeach (QScxmlExecutableContent::EvaluatorId id, bool *ok, QScxmlDataModel::ForeachLoopBody *body).

This method does not perform any action, ignores id and body , and sets ok to false . Override it in your specific data model in order to implement <foreach> .

`[override virtual]` void QScxmlCppDataModel:: evaluateInitialization ( QScxmlExecutableContent::EvaluatorId id , bool * ok )

重實現： QScxmlDataModel::evaluateInitialization (QScxmlExecutableContent::EvaluatorId id, bool *ok).

This method does not perform any action, ignores id , and sets ok to false . Override it in your specific data model in order to implement <data> .

`[override virtual]` bool QScxmlCppDataModel:: hasScxmlProperty (const QString & name ) const

重實現： QScxmlDataModel::hasScxmlProperty (const QString &name) const.

This method always returns false and ignores name . Override it to implement the lookup of data model properties via the location attribute of various elements.

bool QScxmlCppDataModel:: inState (const QString & stateName ) const

返迴 true if the state machine is in the state specified by stateName , false 否則。

const QScxmlEvent &QScxmlCppDataModel:: scxmlEvent () const

Holds the current event that is being processed by the state machine.

另請參閱 SCXML Specification - 5.10 System Variables for the description of the _event 變量。

Returns the event currently being processed.

另請參閱 setScxmlEvent ().

`[override virtual]` QVariant QScxmlCppDataModel:: scxmlProperty (const QString & name ) const

重實現： QScxmlDataModel::scxmlProperty (const QString &name) const.

This method always returns an empty QVariant and ignores name . Override it to implement the lookup of data model properties via the location attribute of various elements.

另請參閱 setScxmlProperty ().

`[override virtual]` void QScxmlCppDataModel:: setScxmlEvent (const QScxmlEvent & event )

重實現： QScxmlDataModel::setScxmlEvent (const QScxmlEvent &event).

設置 event that will be processed next.

另請參閱 QScxmlCppDataModel::scxmlEvent .

`[override virtual]` bool QScxmlCppDataModel:: setScxmlProperty (const QString & name , const QVariant & value , const QString & context )

重實現： QScxmlDataModel::setScxmlProperty (const QString &name, const QVariant &value, const QString &context).

This method always returns false and ignores name , value ，和 context . Override it to implement the lookup of data model properties via the location attribute of various elements.

另請參閱 scxmlProperty ().

`[override virtual]` bool QScxmlCppDataModel:: setup (const QVariantMap & initialDataValues )

重實現： QScxmlDataModel::setup (const QVariantMap &initialDataValues).

Called during state machine initialization to set up a state machine using the initial values for data model variables specified by their keys, initialDataValues . These are the values specified by <param> tags in an <invoke> 元素。

注意： 此函數可以被援引，通過元對象係統和從 QML。見 Q_INVOKABLE .

另請參閱 QScxmlStateMachine::init .

QScxmlCppDataModel Class

公共函數

重實現公共函數

詳細描述

成員函數文檔編製

QScxmlCppDataModel:: QScxmlCppDataModel ( QObject * parent = nullptr)

[override virtual] void QScxmlCppDataModel:: evaluateAssignment ( QScxmlExecutableContent::EvaluatorId id , bool * ok )

[override virtual] void QScxmlCppDataModel:: evaluateForeach ( QScxmlExecutableContent::EvaluatorId id , bool * ok , QScxmlDataModel::ForeachLoopBody * body )

[override virtual] void QScxmlCppDataModel:: evaluateInitialization ( QScxmlExecutableContent::EvaluatorId id , bool * ok )

[override virtual] bool QScxmlCppDataModel:: hasScxmlProperty (const QString & name ) const