c++ - Qt 状态机 : How to associate a single transition with multiple states

Question

问题

我目前正在开发一个使用 Qt 状态机框架的应用程序，我的目标是将单个转换与多个源状态相关联。这样做的理由是导致转换的信号独立于源状态，因此我认为最好有一个而不是多个转换(每个源状态一个)。我在通过 Qt 实现上述目标时遇到了问题。下面使用测试状态机演示了详细信息。 (下面提到的是一个假设的状态机，但我也可以为这种用例提供​​一些真实世界的例子)。请提出一些有效的方法来实现上述目标。

问题所在的代码片段

m_s1.addTransition(&m_Trans); // Adding transition to state S1
m_s2.addTransition(&m_Trans); // Adding the same transition to state S2
                              // As per Qt docs, it seems the ownership of thr transition will be transferred to s2 which is what is causing the problem.

CState.hpp

class CState: public QState
{

public:

    /** Constructor */
    CState(std::string a_pStateName)
       :QState(nullptr),
        m_pStateName(a_pStateName)
    {

    }

    /** Overriding on entry */
    virtual void onEntry(QEvent *a_pEvent) Q_DECL_OVERRIDE
    {
        (void) a_pEvent;
        printf("State entry %s\n",m_pStateName.c_str());
    }

    ~CState() {}
     CState() {}
private:
    std::string  m_pStateName;
};

CTestMachine.hpp

class CTestStateMachine: public QObject
{
    Q_OBJECT

public:
    CTestStateMachine();
    ~CTestStateMachine() {};

private:
    QSignalTransition       m_Trans;
    CState                  m_s1;
    CState                  m_s2;
    CState                  m_s3;
    QStateMachine           m_TestMachine;
    QTimer                  m_Timer;

signals:
    void SourceIndependentSignal();

public slots:
    void TimetoInvokeTrans();


};

CTestMachine.cpp

#include <stdio.h>
#include <iostream>
#include <string>
using namespace std;

#include <QObject>
#include <QCoreApplication>
#include <QStateMachine>
#include <QState>
#include <QSignalTransition>
#include <QTimer>

#include "CState.hpp"
#include "CTestStateMachine.hpp"

void CTestStateMachine::TimetoInvokeTrans()
{
    printf("Emitting source independent signal\n");
    emit SourceIndependentSignal();
}

CTestStateMachine::CTestStateMachine():
    m_Trans(this, SIGNAL(SourceIndependentSignal())),
    m_s1("s1"),
    m_s2("s2"),
    m_s3("s3")
{
   /* Setup state machine */
   m_Trans.setTargetState(&m_s3);
   m_s1.addTransition(&m_Trans);
   m_s2.addTransition(&m_Trans);
   m_TestMachine.addState(&m_s1);
   m_TestMachine.addState(&m_s2);
   m_TestMachine.addState(&m_s3);
   m_TestMachine.setInitialState(&m_s1);
   m_TestMachine.start();
   printf("Started state machine\n");

   /* Trigger timer to make transitions */
   connect(&m_Timer, SIGNAL(timeout()), this, SLOT(TimetoInvokeTrans()));
   m_Timer.start(1000);
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    CTestStateMachine TestMachine;
    return a.exec();
}

Answer 1

您可以在进入状态时移动转换。

connect(m_state, &QState::entered, [m_state, m_tr]() -> void { m_state->addTransition(m_tr); });

或者只是让父状态保持转换并将转换类型设置为内部。

QState *s = new QState(m_stateMachine);
QState *s1 = new QState(s);
QState *s2 = new QState(s);
QState *s3 = new QState(s);
QSignalTransition *sTr = new QSignalTransition(sender, SIGNAL(foobar), s);
sTr->setTargetState(s3);
sTr->setTransitionType(QAbstractTransition::InternalTransition);