QT4没有这样的插槽错误

Question

I know there are many many questions that are just the same, but none of them helps me:

class Form1 : public QMainWindow {
    Q_OBJECT
public:
    Form1();
    virtual ~Form1();
public slots:
    void langChange(const char* lang_label);
private:
    Ui::Form1 widget;
    void setLangStrings();
};

From1 constructor:

Form1::Form1() {
    widget.setupUi(this);
    connect(widget.btnL0, SIGNAL(clicked(bool)), this, SLOT(langChange("en")));
    connect(widget.btnL1, SIGNAL(clicked(bool)), this, SLOT(langChange("fr")));
    setLangStrings();
}

And I also have this langChange function implemented:

void Form1::langChange(const char* lang_label)
{
    GL_LANG = lang_label;
    setLangStrings();
}

I get this stupid error when the connect function is called:

No such slot Form1::langChange("sl") in Form1.cpp:15

I'm using NetBeans with QDesigner for the UI. I must say this QT4 is very difficult to learn.

Answer 1

You simply can't connect SIGNAL with bool as argument to SLOT with const char* as argument. To do this kind of stuff you have to use QSignalMapper . You have an example how to use it inside documentation. In your case, it's very simple, so you should handle it easly.

Answer 2

The SLOT function must have the same signature than the SIGNAL function

Edit: From the official Qt documentation (http://qt-project.org/doc/qt-4.8/signalsandslots.html):

The signature of a signal must match the signature of the receiving slot. (In fact a slot may have a shorter signature than the signal it receives because it can ignore extra arguments.)