Nested QVector problem

[pauledd]

Hi

I currently struggle with a nested QVector.
I need to have a QVector<QCheckbox*> that has 24 Checkboxes
in it representing 24 columns. From this QVector<QCheckbox*> I want to have 5 in a parent Vector representing 5 rows so that I can access them like that

outer.at(4).at(23).setChecked(1)

to access the 24th checkbox in the 5th row. (Of course all this is going later inside a QGridLayout)

But I simply dont get it how to create the two vectors.

I would start by creating them:

QVector<QCheckBox*> inner;
QVector<QVector<QCheckBox*>> outer;

Then I would propably fill the first one with the 24 checkboxes:

for(int i=0;i<24;i++){
		inner.append(new QCheckBox);
	}

But how do I create 5 of them inside the outer vector. I am a bit lost here.

[ODБOï]

@pauledd hi

    for(int i=0;i<5;i++){
            outer.append(inner);
        }

[pauledd]

@LeLev thank you. But if I now try to fill the grid layout with that vector
like that:

        layGrid = new QGridLayout;
	for(int i=0;i<24;i++){
		inner.append(new QCheckBox);

	}

	for(int i=0;i<5;i++){
		outer.append(inner);
	}

	for(int i=0;i<outer.size();i++){
		for(int j=0;j<inner.size();j++){
			layGrid->addWidget(outer.at(i).at(j),i,j);
		}
	}

I get only the first row with checkboxes...

[beecksche]

@pauledd

Why don't you use a QGenericMatrix ?

[pauledd]

@beecksche Because the title says "QVector problem" ;) and I really dont understand https://doc.qt.io/qt-5/qgenericmatrix.html and there are nearly zero examples on the internet

[mrjj]

@pauledd
Hi
Its a logical bug :)
I had to play with the code to realize.

// create one row of checkboxes
auto layGrid = new QGridLayout;
for (int i = 0; i < 24; i++) {
inner.append(new QCheckBox);
}

// copy same row of checkbox to outer 5 times
// BUT since there really is only one row of widgets, we will only see
// 1 row of checkboxes in the layout.
// since we just copy the pointers and the other rows
// shares the listboxes!

for (int i = 0; i < 5; i++) {
    outer.append(inner);
}

so you have to do

 for (int i = 0; i < 5; i++) {
        inner.clear();
        for (int i = 0; i < 24; i++) {
            inner.append(new QCheckBox);
        }
        outer.append(inner); // now we add a new inner and not reuse the same
    }

and then it works

Cheers

[pauledd]

@mrjj Man that drove me crazy, thanks a lot :). I somehow knew there was something wrong adding it to outer because it reserved somehow space for the non-existing rows.

[mrjj]

@pauledd
Yeah, it also got me for a moment.
Same for me as the checkbox row came in the bottom of the layout and then it hit me hard :)

[ODБOï]

@mrjj good catch ^^