trouble connecting private slot to a signal

[mono]

Hello,
I am having trouble connecting my slot to a signal that I want, I might be making some beginner mistake (since I am a beginner) but I can't figure it out even after searching on google for quite a while. Thank you for any help

header file:

private:
    QPushButton *btn_search;
private slots:
    void some_function();
};

in my window.cpp file I am trying to connect the slot to a signal from the btn_search:

window::window(QWidget *parent)
    : QWidget{parent}
{
btn_search = new QPushButton("Search", this);
connect(btn_search, SIGNAL(clicked()), this, SLOT(some_function()));
}

void window::some_function()
{
    /*do something*/
}

I am not getting any errors, but the terminal says this:
QObject::connect: Cannot connect (nullptr)::clicked() to window::combo_by_attribute()

and the button obviously doesn't do anything. I have a lot of other stuff in the program, that work perfectly fine when I run the project. Why I can't connect these two, am I missing something? Thank you

[Christian Ehrlicher]

Your example does not match the output - btn_search is a nullptr when you call connect()

[Pl45m4]

@mono said in trouble connecting private slot to a signal:

btn_search = new QPushButton("Search", this);
connect(btn_search, SIGNAL(clicked()), this, SLOT(some_function()));

The error message looks like your actual code (not the one you show) has these two lines flipped, like:

connect(btn_search, SIGNAL(clicked()), this, SLOT(some_function()));
btn_search = new QPushButton("Search", this);

Also, better switch to the current standard way to establish a connection:

connect(btn_search, &QPushButton::clicked, this, &window::some_function);

[TheoSys]

@mono I suggest to change your code like this:

window::window(QWidget *parent)
    : QWidget{parent}
{
   btn_search = new QPushButton("Search", this);
   connect(btn_search, &QPushButton::clicked, this, &window::some_function);
}

void window::some_function(bool checked)
{
    /*do something*/
}

[mono]

@Pl45m4 Thank you, it was the problem of flipping those two, so indeed a rookie mistake.
I am using some older books to learn Qt, so they use old notation. My projects worked fine every time, is it a problem that I am using that syntax to connect signals and slots? Thanks

[SGaist]

@mono not a problem per se but you are losing on compiler generated error vs runtime debug output.

One of the advantages is that if you modify a signal or a slot and forget to update the counterpart accordingly, you will know something is off at compile time rather than maybe missing it in logs of your application.