Qt状态机框架连接信号

Question

在Qt状态机框架文档中有一个如何设置属性的示例状态激活：

s1->assignProperty(label, "text", "In state s1");
s2->assignProperty(label, "text", "In state s2");
s3->assignProperty(label, "text", "In state s3");

有没有办法在状态激活时连接插槽？就像 s1_buttonclick 仅在 s1 处于活动状态时才会连接，s2_buttonclick 仅在 s2 处于活动状态时才会连接？

Answer 1

您希望连接根据状态机当前所处的状态而有所不同？

我认为您必须使用其他插槽以及 Entered() 和 Exited() 信号自行管理。只需为各州的每个入口和出口创建一个插槽即可。

QObject::connect(s1, SIGNAL(entered()), connectionManager, SLOT(connectS1()));
QObject::connect(s1, SIGNAL(exited()), connectionManager, SLOT(disconnectS1()));
//continue for each state

Answer 2

可以使用代表连接并提供连接的活动属性的辅助类来完成过滤信号槽连接。请注意，Qt 5 的 QMetaObject::Connection 对此还不够。

#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);
    }
};