- class QScxmlCppDataModel¶
The
QScxmlCppDataModel
class is a C++ data model for a Qt SCXML state machine. More…Synopsis¶
Methods¶
def
__init__()
def
inState()
def
scxmlEvent()
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description¶
The C++ data model for SCXML lets you write C++ code for expr attributes and
<script>
elements. The data part of the data model is backed by a subclass ofQScxmlCppDataModel
, 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 attribute of the
<scxml>
element:<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 ofQScxmlCppDataModel
, 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("media")).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 thethis
pointer is also captured, you can call or access the data model (the media attribute in the example above). For the full example, see SCXML Media Player .See also
Creates a new C++ data model with the parent object
parent
.- inState(stateName)¶
- Parameters:
stateName – str
- Return type:
bool
Returns
true
if the state machine is in the state specified bystateName
,false
otherwise.- scxmlEvent()¶
- Return type:
Holds the current event that is being processed by the state machine.
See also SCXML Specification - 5.10 System Variables for the description of the
_event
variable.Returns the event currently being processed.
See also
setScxmlEvent()