Qt state machine framework connect signals - qt

Question

In the Qt State Machine Framework documentation there is an example how to set properties on state activation:
s1->assignProperty(label, "text", "In state s1");
s2->assignProperty(label, "text", "In state s2");
s3->assignProperty(label, "text", "In state s3");
Is there a way to connect slots on state activation? like s1_buttonclick will only be connected when s1 is active and s2_buttonclick will only be connected when s2 is active?

Answer 1

You want the connections to be different based on which state the state machine is currently in?
I think you will have to manage this yourself using other slots and the entered() and exited() signals. Just create a slot for the each entrance and exit of the states.
QObject::connect(s1, SIGNAL(entered()), connectionManager, SLOT(connectS1()));
QObject::connect(s1, SIGNAL(exited()), connectionManager, SLOT(disconnectS1()));
//continue for each state

Answer 2

Filtering signal-slot connections can be done using a helper class that represents a connection and provides an active property of the connection. Note that Qt 5's QMetaObject::Connection is not sufficient for this.
#include <QMetaMethod>
#include <QPointer>
class Connection : public QObject
{
Q_OBJECT
Q_PROPERTY(bool active READ isActive WRITE setActive NOTIFY activeChanged USER true)
Q_PROPERTY(bool valid READ isValid)
QMetaMethod m_signal, m_slot;
QPointer<QObject> m_source, m_target;
#if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
QMetaObject::Connection m_connection;
#else
bool m_connection;
#endif
bool m_active;
void release() {
if (!m_source || !m_target) return;
#if QT_VERSION >= QT_VERSION_CHECK(5,0,0)
disconnect(m_connection);
#else
disconnect(m_source, m_signal, m_target, m_slot);
#endif
}
public:
Connection(QObject * source, const char * signal, QObject * target, const char * slot, QObject * parent = 0) :
QObject(parent),
m_signal(source->metaObject()->method(source->metaObject()->indexOfSignal(signal))),
m_slot(target->metaObject()->method(target->metaObject()->indexOfSlot(slot))),
m_source(source), m_target(target),
m_connection(connect(m_source, m_signal, m_target, m_slot)),
m_active(m_connection)
{}
~Connection() { release(); }
QObject* source() const { return m_source; }
QObject* target() const { return m_target; }
QMetaMethod signal() const { return m_signal; }
QMetaMethod slot() const { return m_slot; }
bool isActive() const { return m_active && m_source && m_target; }
bool isValid() const { return m_connection && m_source && m_target; }
Q_SIGNAL void activeChanged(bool);
Q_SLOT void setActive(bool active) {
if (active == m_active || !m_source || !m_target) return;
m_active = active;
if (m_active) {
m_connection = connect(m_source, m_signal, m_target, m_slot);
} else {
release();
}
emit activeChanged(m_active);
}
};