on Dialog box show() is not working but exec() is

rupertrupert

@Pl45m4 Yeah I was using while loop with sleep() because I needed a way to update something every second, so im not sure what else to do to implement this

rupertrupert

@Pl45m4
Here is what I have right now, allthough update() is never called and I have no idea why
void Object::start(){
ui = new Object2 (nullptr);
ui->open();
QTimer *timer = new QTimer(this);

QObject::connect(timer,SIGNAL(timeout()),this,SLOT(update()));

timer->start(1000);

}

void Object::update(){
qInfo("Hi");
}

Pl45m4

@rupertrupert said in on Dialog box show() is not working but exec() is:

update() is never called and I have no idea why

Because your signal calls QWidget::update() and not your Object::update() function.

https://doc.qt.io/qt-6/qwidget.html#update

Rename your function to something like sayHi() and it should work like expected

Btw: you are leaking memory cause you create a new instance of Object2 every time Object::start() is called. And since your dialog has no valid parent it's not using the auto-cleanup from Qt MetaObject system.

Add Qt::WA_DeleteOnClose as attribute to your dialog or create in just once in your c'tor, then only open/show it when you need it.

JonB

@Pl45m4 said in on Dialog box show() is not working but exec() is:

Because your signal calls QWidget::update() and not your Object::update() function.

Although this would explain behaviour, OOI what makes you say QWidget::update() will be called? The slot is on this, which is a Object with its own update(), and what makes you think Object is a QWidget?

Doubtless @Pl45m4 will turn out to be right though I'm not sure why/how he knows. Otherwise what is the scope/lifetime of the Object instance that start() is called on? Or, again, after start() do you allow the event loop to be re-entered?

Pl45m4

@JonB said in on Dialog box show() is not working but exec() is:

OOI what makes you say QWidget::update() will be called?

The described behavior by OP

The slot is on this, which is a Object with its own update()

True, but OP uses the String-based connections which are not fully qualified and don't specify a type or class.
From my own experience I'm 99.99% sure ;-)

what makes you think Object is a QWidget?

Must be, otherwise it would have worked ;-)
[Edit: Apparently it's actually a QObject but some other weird stuff is going on. Maybe app quit?!]

Btw:
Using a fully qualified functor will also solve this:

// Object::update(), correct
QObject::connect(timer, &QTimer::timeout, this, &Object::update);
// QWidget::update(), wrong
QObject::connect(timer, SIGNAL(timeout()), this, SLOT(update()));

&Object::update will explicitely pick void Object::update() by function reference, which prints "Hi" in this case.
While the String/Macro based syntax just sends a update() call to this without any checks at runtime, which results in QWidget::update() being called.

rupertrupert

@Pl45m4 OK i tried both of the solutions you said and they did not work

Pl45m4

@rupertrupert said in on Dialog box show() is not working but exec() is:

OK i tried both of the solutions you said and they did not work

If the below code does not work, you are still blocking the signal with some sleep or while - loop.
You must not have any sleep or blocking loops in your main/GUI thread in your entire program... otherwise it breaks event driven mechanics as used in Qt.

void Object::start()
{
    ui = new Object2(this);
    ui->open();
    QTimer *timer = new QTimer(this);
    QObject::connect(timer, &QTimer::timeout, this, &Object::update);
    timer->start(1000);
}

rupertrupert

@Pl45m4 said in on Dialog box show() is not working but exec() is:

QObject::connect(timer, &QTimer::timeout, this, &Object::update);

ok I changed to exactly this and now i dont see my ui or anything and the program just closes when I reach Object::start(), and there is no code after Object::start() is called to be blocking the signal

Pl45m4

@rupertrupert said in on Dialog box show() is not working but exec() is:

there is no code after Object::start()

Where do you call start()? In MainWindow? Or in your main.cpp?

How is your Object created and what kind of class is this? As @JonB was also wondering...

rupertrupert

@Pl45m4 after my main window is closed, in the signal that closes it, and it is a QObject

Pl45m4

@rupertrupert said in on Dialog box show() is not working but exec() is:

after my main window is closed

Usually your program would end at this point...
Post the related code then... this isn't a Q&A game here.
We can't see what your are doing exactly