How to reference code created QPushButton?

legitnameyo

I've created a button like this

QPushButton *btn = new QPushButton(ui->frame_btn);

now, how do I reference this? I usually do

ui->btn->move(x, y);

but there is no btn in ui, there is no btn in frame_btn, there is no btn in ui->frame_btn->btn. Where is it and how do I reference it?

JonB

@legitnameyo
If you haven't added it into ui, your code as shown is just creating a variable (local to function by the look of it) so you'd just reference it via plain btn (assuming you're in the function where you've created it).

Pablo J. Rogina

@legitnameyo said in How to reference code created QPushButton?:

Where is it
it'll live in the scope of where you create it (i.e. class, method). You need to provide a bigger code snippet to be sure where you're creating it

and how do I reference it

btn->move(x, y);

you've just created a pointer to a QPushButton

there is no btn in frame_btn

No, frame_btn is just the parent object of your btn object

legitnameyo

I created it where basically everything is located, in the main widget. I am referencing it from another function.

legitnameyo

This is what I want to do

test::test(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::test)
{
    ui->setupUi(this);
    QPushButton *btn = new QPushButton(ui->frame_btn);
}

void test::move_btn() {
    ui->frame_btn->btn->move(25, 25); // there is no "btn" in ui->frame_btn, gives error
}

is there a way to reference the button???

Cobra91151

@legitnameyo

Hi! You can add QPushButton *btn to your header file, for example - test.h (toprivate section). Then you can use your button everywhere in your class. But don't forget this is a pointer, so you should call btn->deleteLater() or delete btn in the destructor to free resources, so no memory leak occur in your application.

Also note by using Forms it creates the namespace - ui which handles the access/destruction of your widgets, added on the graphical form.

Happy coding!

Pablo J. Rogina

@legitnameyo

is there a way to reference the button???

as mentioned by @Cobra91151 make it a member of your class test (BTW, it's a common practice to name your Classes using uppercase

you should call btn->deleteLater() or delete btn in the destructor to free resources

No need to do that you if you make the class the parent of the button, i.e. (assuming btn is a member of class Test

test.h

...
private:
QPushButton *btn;
...

test.cpp

...
Test::Test(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::test)
{
    ui->setupUi(this);
    btn = new QPushButton(this);
}
...

legitnameyo

Doing what @Pablo-J-Rogina said made it possible to reference it, but when I do and try to move it, the program crashes:

The program has unexpectedly finished.
The process was ended forcefully.

I referenced it as

btn->move(25, 25);

Cobra91151

@legitnameyo

I think your program crashes because it initializes two pointers. Remove QPushButton * from your constructor. It should be:

test.h

private:
QPushButton *btn;

test.cpp

Test::Test(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::test)
{
    ui->setupUi(this);
    btn = new QPushButton(this);
}

Also try to attach the debugger and run your program, it should detect the issue.