Signal / Socket connection problem...

[KroMignon]

@SPlatten said in Signal / Socket connection problem...:

I have written a class which is derived from QPushButton, in my derived class I want to connect the "clicked" signal to a slot in the same class also called "clicked". In my derived class:
private slots:
void clicked(bool blnChecked);

I don't think it is a good idea to have a signal and a slot have same name!

I would remane slot to

private slots:
    void clicked(bool blnChecked);

And use new connection syntax to got connection failures at compilation time and not runtime:

connect(this, &MyButton:clicked, this, &MyButton:onClicked);

And don't forget to add "Q_OBJECT":

class MyButton : QPushButton
{
   Q_OBJECT
...
private slots:
    void clicked(bool blnChecked);
}

And perhaps also rerun qmake

Regards

[jsulm]

@SPlatten said in Signal / Socket connection problem...:

QObject::connect: No such slot QPushButton::clicked(bool)

Are you sure this warning comes from the connect you pasted here?
Because the warning should be

QObject::connect: No such slot YOURCLASSNAME::clicked(bool)

Are you trying to connect somewhere else also?
And is the warning now exact the same or does it contain the new slot name?

[SPlatten]

@KroMignon, thank you, adding Q_OBJECT to my derived class has stopped the warning from being displayed, however when I click the button I still don't see anything in the slot which I've now renamed to "clickedHandler"

@jsulm, yes, positive, its the only connect I have.

[Pradeep P N]

Hi @SPlatten

Even using

private slots:
    void clicked(bool);

Works fine for me.

Below is my code

#include <QPushButton>

class Widget : public QPushButton
{
    Q_OBJECT

public:
    Widget(QPushButton *parent = nullptr);
    ~Widget();

private slots:
    void clicked(bool);
};

Widget::Widget(QPushButton *parent)
    : QPushButton(parent)
{

    // New syntax
    // connect(this, &Widget::clicked, this, &Widget::clicked);

    // Old syntax
     connect(this, SIGNAL(clicked(bool)), this, SLOT(clicked(bool)));
}

void Widget::clicked(bool)
{
    qDebug() << Q_FUNC_INFO << endl;
}

[jsulm]

@SPlatten said in Signal / Socket connection problem...:

I still don't see anything in the slot

What do you mean by that? What are you doing in the slot?

[Pradeep P N]

@SPlatten Please check with

connect(this, SIGNAL(clicked(bool)), this, SLOT(clicked(bool)));

It works.

There is no issue in Build but still the Slot is not called when using new connect syntax.

[KroMignon]

@SPlatten said in Signal / Socket connection problem...:

still don't see anything in the slot which I've now renamed to "clickedHandler"

What do you mean? Is the slot not called? Are you sure you are watching/click on the right button?

[SPlatten]

Ok, I've now got it working and just for the record and anyone else needing do so the same, this is what I needed to do. I thought 'wrongly' that because my class was derived from QPushButton which already has Q_OBJECT in it, that I didn't need to do the same, wrong!

Adding Q_OBJECT to the class solved the problem. Also having a signal and slot with the same name does not cause a problem, it's quite possible to have both with the exact same name.

My class, still a work in progress but working:

    class clsMenuBtn;
    typedef List<clsMenuBtn*> lstOfMenus;

    class clsMenuBtn : public QPushButton {
    Q_OBJECT

    private:
        bool mblnSecure;
        clsMenuBtn* mpChildren, *mpNext, *mpParent, *mpPrev;

    public slots:
        void clicked(bool blnChecked);

    public:
        clsMenuBtn(QString strText = "", QWidget* pobjParent = NULL
                                       ,bool blnSecure = false);
        lstOfMenus lstGetMenus();
        clsMenuBtn* pAddOption(QString strText = "", bool blnSecure = false);
        clsMenuBtn* pGetChildren() { return mpChildren; }
        clsMenuBtn* pGetNext() { return mpNext; }
        clsMenuBtn* pGetParent() { return mpParent; }
        clsMenuBtn* pGetPrev() { return mpPrev; }
        void setText(const QString& strText);
    };

[KroMignon]

@SPlatten said in Signal / Socket connection problem...:

Adding Q_OBJECT to the class solved the problem

When you are creating a class which is based on QObject and you want to add new signals and/or slots, you have to add Q_OBJECT macro to enable "MOC magic". That is mandatory!

[SPlatten]

As I said, I thought wrongly that since my class was derived from one with that functionality already present, that my new class would inherit the same, live and learn :)

[Pradeep P N]

@SPlatten
Also here is the reason why new connect syntax donot work in this case.

https://wiki.qt.io/New_Signal_Slot_Syntax#Overload

[J.Hilk]

@SPlatten
also in case you didn't do it. Initializing the "parent QObject-class" in the constructor is a good practice you should always do.

[SPlatten]

I do, my code for the implementation of the constructor:

    /**
     * @brief clsMenuBtn::clsMenuBtn
     * @param strText          Optional, text for menu
     * @param pobjParent  Optional, pointer to parent object
     * @param blnSecure    Optional, secure flag default is false
     */
     clsMenuBtn::clsMenuBtn(QString strText, QWidget* pobjParent, bool blnSecure) : QPushButton(pobjParent) {
         mblnSecure = blnSecure;
         mpChildren = mpNext = mpParent = mpPrev = NULL;
         setText(strText);

         if ( strText.isEmpty() != true ) {
             QObject::connect(this, SIGNAL(clicked(bool)), this, SLOT(clicked(bool)));
         } 
     }