如何识别插槽中发出的信号？

Question

我将两个信号连接到同一个插槽。像这样：

check = new QCheckBox();
connect(check, SIGNAL(clicked()), this, SLOT(MySlot()));
connect(check, SIGNAL(toggled(bool)),this,SLOT(MySlot()));

我不想定义其他插槽。在 MySlot 中是否可以识别哪个信号回调插槽？我怎样才能做到这一点？

Answer 1

您或许可以使用与发件人关联的 QMetaObject/QMetaMethod 数据来获取您想要的内容（未经测试）...

void MyClass::MySlot ()
{
  auto index = senderSignalIndex();
  if (index == sender()->indexOfSignal("clicked()")) {

    /*
     * Got here as the result of a clicked() signal.
     */
  } else if (index == sender()->indexOfSignal("toggled(bool)")) {

    /*
     * Got here as the result of a toggled(bool) signal.
     */
  }
}

但是，如果您使用的是 Qt5，我建议您使用新的 signal/slot 语法和 lambdas...

check = new QCheckBox();
connect(check, &QCheckBox::clicked,
        [this]()
        {
          MySlot(false);
        });
connect(check, &QCheckBox::toggled,
        [this](bool toggled)
        {
          MySlot(true, toggled);
        });

连同对 MySlot 签名的更改...

/**
 * @param from_toggled_signal If true this call was triggered by a
 *                            QCheckBox::toggled signal, otherwise it's
 *                            the result of a QCheckBox::clicked signal.
 *
 * @param toggle_value If from_toggled_signal is true then this was the
 *                     value passed to QCheckBox::toggled, otherwise unused.
 */
void MyClass::MySlot (bool from_toggled_signal, bool toggle_value = false)
{
  .
  .
  .
}

Answer 2

可以使用 lambda 动态定义新槽 :)

class MyClass : public QWidget {
  QSomeLayout m_layout{this};
  QCheckBox m_check;
  enum Signal { Clicked, Toggled };

  Q_SLOT void mySlot(Signal);
public:
  MyClass( ... ) : ... {
    m_layout.addWidget(&m_check);
    connect(&m_check, &QCheckBox::clicked, this, [this]{ mySlot(Clicked); });
    connect(&m_check, &QCheckBox::toggled, this, [this]{ mySlot(Toggled); });
  }
};

Answer 3

如果有帮助，您还可以将自己的上下文添加到信号中。例如，我有一项服务可以为多个 windows 下载用户头像。我需要 window 只加载它感兴趣的用户，所以我会传入用户的 ID 作为上下文。类似于：

void UserService::downloadAvatar(const QString& url, const int context = 0) {
  ...// Make the http request, on finished:

  emit onAvatarDownloaded(context, responseBody);

}

如何识别插槽中发出的信号？

how to recognize which signal emitted in slot?

c++

qt

slot

qt-signals