Connect() uses wrong emitter object.

Kalado

Hallo,
I am having a problem with a connection and need some help.
So I have one class A being utilized in another class B.
I would like to connect a SIGNAL from A to a SLOT from B, within B.

Look at some code:

//A.h
class task2 : public QWidget
{
    Q_OBJECT
public:
    task2(QWidget *parent = 0);
    ~task2();
protected:
    void mousePressEvent(QMouseEvent *event) override;
signals:
    void  myWidgetClicked();

//A.cpp
void A::mousePressEvent(QMouseEvent *event){
    emit myWidgetClicked();
}

I have a different connection in A using this SIGNAL within and without problems.

B.h
#include <A.h>
QT_BEGIN_NAMESPACE
class A;
QT_END_NAMESPACE
class B : public QMainWindow
{
    Q_OBJECT
private:
    A *a;
    void myFunction();
private slots:
    void doSomething();

//B.cpp
B::B() : a (new A){
    myFunction();
}

void B:myFunction(){
    connect(a,SIGNAL(myWidgetClicked()),this,SLOT(doSomething()));
}

B is being shown in the main.cpp.

I don't know why this doesn't work.

Console says :

QObject::connect: No such signal B::myWidgetClicked()

But I entered "a" as the emitter.
Any help would be much appreciated.

Kind regards,
Karim

joeQ

@Kalado Hi,friend,welcome .

You write wrong name of signal.

signals:
    void  myWidgetClicked(); ///< this is your A's signal define

But,

void B:myFunction(){
    connect(a,SIGNAL(myWidgetC L icked()),this,SLOT(doSOmething())); ///< Notes the spelling error ‘L’ => 'l'
}

Kalado

Hi joe,
unfortunately this error is in this post only, the source code is without spelling errors.

artwaw

Have you tried to make slot public instead of private?

taedium

@Kalado In principal it should work. Please paste your actual code, that at least compiles.

Pradeep Kumar

Hi,

@Kalado

try the below code, to have a signal emitted from one class to another,

"A.h"

class A : public QWidget
{
    Q_OBJECT

public:
    A(QWidget *parent = 0);
    ~A();


    B *m_second;

    void mousePressEvent(QMouseEvent *event) override;

signals:
    void  myWidgetClicked();
};

"A.cpp"

A::A(QWidget *parent)
    : QWidget(parent)
{
    m_second = new B;
    connect(this,SIGNAL(myWidgetClicked()),m_second,SLOT(getEventSlot()));
}

void A::mousePressEvent(QMouseEvent *event)
{
    qDebug () << "mouse clicked :" << endl;
    emit myWidgetClicked();
}

"B.h"

class B : public QWidget
{
    Q_OBJECT
public:
    explicit B(QWidget *parent = 0);

signals:

public slots:
    void getEventSlot();
};

"B.cpp"

B::B(QWidget *parent) : QWidget(parent)
{
}

void B::getEventSlot()
{
    qDebug () << Q_FUNC_INFO << "event came to slot of Class B on mouse clicked :" << endl;
}

Thanks,

Pradeep Kumar

@Kalado said in Connect() uses wrong emitter object.:

Look at some code:

//A.h
class task2 : public QWidget
{
    Q_OBJECT
public:
    task2(QWidget *parent = 0);
    ~task2();
protected:
    void mousePressEvent(QMouseEvent *event) override;
signals:
    void  myWidgetClicked();

//A.cpp
void A::mousePressEvent(QMouseEvent *event){    /// use the respective classname
    emit myWidgetClicked();
}

If ur using Classname as task2 , use

void task2::mousePressEvent(QMouseEvent *event){
    emit myWidgetClicked();
 }

Thanks,