connect to a signal

viniltc

Hi all,

I'm trying to connect to a signal as follows

 connect(&api, SIGNAL(tetraGripEvent()), this, SLOT(eventHandler()));

But it says No such signal tetra_grip_api::tetraGripEvent(), let me explain the scenario:

I have defined the signal in a class called tetra_grip_api as follows:

void tetra_grip_reporter(STIM_GUI_TOPIC_T topic, uint8_t reg, uint32_t value)
{
    emit api.tetraGripEvent(topic, reg, value);
}

where tetra_grip_reporter need to be called from a c file, so I defined it as:

#ifdef __cplusplus
extern "C" {
#endif

void tetra_grip_reporter(STIM_GUI_TOPIC_T topic, uint8_t reg, uint32_t value);

#ifdef __cplusplus
}
#endif

I don't know where I'm wrong. Any help would be welcome.

Thanks in advance

jsulm

@viniltc You need to have tetraGripEvent declared as signal in tetra_grip_api:

class tetra_grip_api : public QObject
{
    Q_OBJECT
signals:
    void tetraGripEvent();
}

The class has to be derived from QObject and have Q_OBJECT macro. See https://doc.qt.io/qt-5/signalsandslots.html
Does it look like this in your code?

jsulm

@viniltc said in connect to a signal:

I have defined the signal in a class called tetra_grip_api as follows:

And this is not a definition of a signal. Here you emit the signal.
Also, you're passing 3 parameters to the signal but in the connect your signals/slots do NOT have any parameters.

viniltc

@jsulm Thanks for your reply.
Yes, I defined the signal as follows:

class tetra_grip_api : public QObject
{
    Q_OBJECT
signals:
    void tetraGripEvent(STIM_GUI_TOPIC_T topic, uint8_t reg, uint32_t value);

jsulm

@viniltc Then your connect is wrong as you have not specified any parameters there.

viniltc

@jsulm
Do you mean to define as follows?

connect(&api, SIGNAL(tetraGripEvent(topic, reg, value)), this, SLOT(eventHandler()));

jsulm

@viniltc said in connect to a signal:

Do you mean to define as follows?

No

connect(&api, SIGNAL(tetraGripEvent(STIM_GUI_TOPIC_T, uint8_t, uint32_t)), this, SLOT(eventHandler(STIM_GUI_TOPIC_T, uint8_t, uint32_t)));

You have to specify the types of the parameters.
See the link I gave you.

viniltc

@jsulm Thanks a lot for your feedback! That's fixed