dynamically unknown size of label array

Hi,

I'm a newbie for Qt C++. I want to create the QLabels Array programmatically.
It's ok. code is as follow:

Code:

---

#ifndef MYWIDGET_H
#define MYWIDGET_H
 
#include <QWidget>
#include <QLabel>
 
class MyWidget : public QWidget
{
    Q_OBJECT
 
public:
    MyWidget(QWidget *parent = 0);
    ~MyWidget();
 
private:
    QLabel *mylabel[5];
 
};
 
#endif // MYWIDGET_H

---

Code:

---

#include "mywidget.h"
 
#include <QLabel>
#include <QVBoxLayout>
 
MyWidget::MyWidget(QWidget *parent)
    : QWidget(parent)
{
    QVBoxLayout *layout = new QVBoxLayout;
    int i;
 
    for(i=0;i<5;i++)
    {
        mylabel[i] = new QLabel("Title: " + QString::number(i+1));
        layout->addWidget(mylabel[i]);
    }
    this->setLayout(layout);
 
}

---

This code created 5 label
But I want to create labels that numbers is assigned when I call class.
My Question is how to assign number of labels to create dynamically?

just example:

Code:

---

#include "mywidget.h"
 
int main(int argc, char *argv[])
{
    MyWidget mytitle(3); // create 3 labels
    MyWidget mysubtitle(10); // create 10 labels
 
 
    return 0;
}

---

Another Question is Array can resize and created programmatically.
I created it in VB just like:

Code:

---

dim A() as string
.....
 
ReDim A(1)
 
Dim i as Integer
i = UBound(A) + 1
ReDim Preserve A(i)

---

If yes, how to do it?

Thanks in advance.

(1) Make the number of labels a parameter of MyWidget ctor:

Code:

---

class MyWidget : public QWidget
{
  Q_OBJECT
 
  public :
    MyWidget( int howmany, QWidget *parent = 0 );
 
    ...
};

---

then you can use the syntax shown in your post.

(2) Use QVector<MyWidget *> instead of a "plain" array. You'll be able to resize or remove existing vector items.

thanks for your replay.

eg. how to assign parameter (eg howmany) as array size?
I change code as follow: It gives error.

Code:

---

class MyWidget : public QWidget
{
    Q_OBJECT
 
public:
    MyWidget(int howmany, QWidget *parent = 0);
    ~MyWidget();
 
private:
    int n;
    QLabel *mylabel[n];
 
};
 
#endif // MYWIDGET_H

---

Code:

---

#include "mywidget.h"
 
#include <QLabel>
#include <QVBoxLayout>
 
MyWidget::MyWidget(int howmany, QWidget *parent)
    : QWidget(parent), h(howmany)
{
    QVBoxLayout *layout = new QVBoxLayout;
    int i;
 
    for(i=0;i<n;i++)
    {
        mylabel[i] = new QLabel("Title: " + QString::number(i+1));
        layout->addWidget(mylabel[i]);
    }
    this->setLayout(layout);
 
}

---

compiler give error:
mywidget.h:39: error: invalid use of non-static data member 'MyWidget::n'
int n;
^

Don't use an array. Use QVector or QList as Radek said. Both of them don't need initial size.

Thanks Radek and Lesiok.

I changed from array to QList. I got it.

(1) The error: You cannot declare a "plain" array with a variable size

Code:

---

private:
int     n;
QLabel *mylabel[n];    // compile error

---

Tne n needed be an initialized const int.

(2) IMO, QVector is better here. QVector is a dynamic array while QList is a linked list. Nevertheless both of them will serve you good.

QList is not a linked list, but I agree that QVector is more appropriate here since the length is already known at creation time.

Cheers,
_