qt give an ui component to an object function

Question

I want to create an object function that changes the color of a certain pushbutton. I would like to give an ui->pushbutton to it.

So I would be calling the function with something like this:

changeButtonColor(ui->pushbutton);

How do I need to write the function?

void MainWindow::changeButtonColor(ui->pushbutton)
{
}

what is your question? do you know how to define a function that takes eg an `int` as parameter? — 463035818_is_not_an_ai, Sep 10 '19 at 09:44
This code is not legal C++. A method definition expects a type, not an object. — BDL, Sep 10 '19 at 12:41

score 0 · Accepted Answer · edited Sep 10 '19 at 18:01

0

If you want to modify the pushbutton in the function you have two options to pass it as an argument to a function: as a pointer, or as a reference. In each case, the function signature (prototype) would be:

Pointer parameter:

void MainWindow::changeButtonColor(QPushButton * button);

Reference parameter:

void MainWindow::changeButtonColor(QPushButton & button);

In each case, a call to the function would be:

Pointer argument:

changeButtonColor(ui->pushbutton);

Reference argument:

changeButtonColor(*ui->pushbutton);

More information: difference between a pointer and reference parameter?

edited Sep 10 '19 at 18:01

463035818_is_not_an_ai

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answered Sep 10 '19 at 10:15

Former contributor

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how about passing values? – 463035818_is_not_an_ai Sep 10 '19 at 14:15
@formerlyknownas_463035818 if you could pass a pushbutton by value to a function, then you could not change the button color with this function. – Former contributor Sep 10 '19 at 16:37
A more general explanation to the question why you can't pass a pushbutton object by value to a function is that all QWidgets derive from QObject, which has the copy constructor and assignment operator disabled. [More information here](https://stackoverflow.com/questions/19092513/copy-constructor-of-derived-qt-class). – Former contributor Sep 10 '19 at 16:48
might be true for pushbuttons and this question, but you start with "In C++, you have two options to pass an object as an argument to a function:" – 463035818_is_not_an_ai Sep 10 '19 at 17:18
Fixed the answer to delimit the scope. I've also edited the question to improve its inteligibility (pending of peer review) – Former contributor Sep 10 '19 at 17:23
made an edit. Its just a suggestion.... – 463035818_is_not_an_ai Sep 10 '19 at 18:02

qt give an ui component to an object function

1 Answers1