Dynamic For generation Problems.

[ShapeShiftme]

Good day all.
This post is an addon to a previous one where i had trouble creating the layout but not that is sorted. Here is my problem

I have a list of 3 items that i would like edited "They happen to corrispond to database field in mysql"
The amount of items can change so therefore i dont want to create the form statically then i would have to create 35 forms in stead of just 1 and pass the list to it.

So this is what i have got to create the form "Im not using a ui as it must be dynamic"

.h file

#ifndef FRM_MAINTENANCE_ALL_H
#define FRM_MAINTENANCE_ALL_H
 
#include <QWidget>
#include <QDialog>
#include <QtGui>
#include <QApplication>
#include <QDebug>
#include <QMessageBox>
#include <QList>
 
class frm_maintenance_all : public QWidget
{
    Q_OBJECT
public:
    explicit frm_maintenance_all(QWidget *parent = 0);
 
signals:
 
public slots:
 
private slots:
    void frm_create(QString tablename);
    void btn_process();
 
private:
 
 
 
};
 
#endif // FRM_MAINTENANCE_ALL_H

#ifndef FRM_MAINTENANCE_ALL_H
#define FRM_MAINTENANCE_ALL_H

#include <QWidget>
#include <QDialog>
#include <QtGui>
#include <QApplication>
#include <QDebug>
#include <QMessageBox>
#include <QList>

class frm_maintenance_all : public QWidget
{
    Q_OBJECT
public:
    explicit frm_maintenance_all(QWidget *parent = 0);
    
signals:

public slots:

private slots:
    void frm_create(QString tablename);
    void btn_process();

private:



};

#endif // FRM_MAINTENANCE_ALL_H

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.cpp file

#include "frm_maintenance_all.h"
 
frm_maintenance_all::frm_maintenance_all(QWidget *parent) :
    QWidget(parent)
{
    frm_create("test");
 
}
 
void frm_maintenance_all::frm_create(QString tablename)
{
 
    QVBoxLayout *myhoz = new QVBoxLayout;
    QStringList mylist;
    mylist<< "description" << "name" << "id";
 
    int i;
    QLineEdit *myline;
    for(i=1;i<=mylist.length();i++)
    {
       myline = new QLineEdit;
       myline->setText("Text " + QString::number(i)); //just setting text for testing
       myhoz->addWidget(myline);
    }
 
    QPushButton *btn_process_form = new QPushButton;
    myhoz->addWidget(btn_process_form);
 
    setLayout(myhoz);
    btn_process_form->setText(myline->text()); //it set the text to the last loop as expected but would like to be able to choose which box i want
    connect(btn_process_form,SIGNAL(clicked()),this,SLOT(btn_process()));
 
    setWindowTitle("Test");
    show();
 
}
 
void frm_maintenance_all::btn_process()
{
         //This does not work (expected to show line 3 option).
        qDebug()<< myline->text();
 
        //this function fails left uncomented here for reading
        QLineEdit* mydyline = parentWidget()->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = parent()->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = this->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        //FAILS WITH THIS ERROR
        //The program has unexpectedly finished.
 
}

#include "frm_maintenance_all.h"

frm_maintenance_all::frm_maintenance_all(QWidget *parent) :
    QWidget(parent)
{
    frm_create("test");

}

void frm_maintenance_all::frm_create(QString tablename)
{

    QVBoxLayout *myhoz = new QVBoxLayout;
    QStringList mylist;
    mylist<< "description" << "name" << "id";

    int i;
    QLineEdit *myline;
    for(i=1;i<=mylist.length();i++)
    {
       myline = new QLineEdit;
       myline->setText("Text " + QString::number(i)); //just setting text for testing
       myhoz->addWidget(myline);
    }

    QPushButton *btn_process_form = new QPushButton;
    myhoz->addWidget(btn_process_form);

    setLayout(myhoz);
    btn_process_form->setText(myline->text()); //it set the text to the last loop as expected but would like to be able to choose which box i want
    connect(btn_process_form,SIGNAL(clicked()),this,SLOT(btn_process()));

    setWindowTitle("Test");
    show();

}

void frm_maintenance_all::btn_process()
{
         //This does not work (expected to show line 3 option).
        qDebug()<< myline->text();

        //this function fails left uncomented here for reading
        QLineEdit* mydyline = parentWidget()->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = parent()->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        // this also fails
        QLineEdit* mydyline = this->findChild<QLineEdit*>("myline");
        qDebug()<< mydyline->text();
        //FAILS WITH THIS ERROR
        //The program has unexpectedly finished.

}

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So there are 2 things i would like to please know :

1) How can i create a unique id or something for the LineEdit so i can reference it
eg so i could set the push button to line 2's text instead of the last one.

2) How do i then access the values From sub Functions

Help with this regard Will be awsome

Thanks very much

[ChrisW67]

Your code as presented will not compile. "myline" at cpp line 41 is not declared anywhere. Given that you seem to have had it compile you must have a "myline" declared as a member variable that you did not show us. This variable is in no way related to the "myline" variable declared at line 18 and used in the function frm_create(). Your compiler is probably warning you that the "myline" in frm_create() masks an earlier definition.

Line 41 crashes because myline is null or invalid.
Line 44 can crash because parentWidget() is null. If it doesn't crash for that reason then it will return null because you have not called setObjectName() on any of your widgets, so there is no widget named "myline". This will make line 45 crash.
Ditto line 47, 50, and 53.

1) How can i create a unique id or something for the LineEdit so i can reference it
eg so i could set the push button to line 2's text instead of the last one.

Keep a pointer to the widget as a member variable and access the widget through its pointer.

2) How do i then access the values From sub Functions

You access member and local variables by name.
If the variable is an object (or reference to one) you can access its member functions using object.function() notation.
If the variable is a pointer to an object then you can access its member functions using object->function() notation.
You can only access variables that are in scope.

All of this is basic C++ and nothing particularly to do with Qt.

[ShapeShiftme]

Line 41 crashes because myline is null or invalid.
Line 44 can crash because parentWidget() is null. If it doesn't crash for that reason then it will return null because you have not called setObjectName() on any of your widgets, so there is no widget named "myline". This will make line 45 crash.
Ditto line 47, 50, and 53.

I understand why they crashed this was more of an eample of what im trying to do do and was hoping for the correct syntax to use

Keep a pointer to the widget as a member variable and access the widget through its pointer.

Could you please give me a small example for this

If the variable is a pointer to an object then you can access its member functions using object->function() notation.

Perhaps an example for this too please.

Regards

[ChrisW67]

#include <QtGui>
#include <QDebug>
 
class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
        QWidget *central = new QWidget(this);   // central is a local varaibale
        label1 = new QLabel(this);  // label1 is a member variable, a pointer to a label
        label2 = new QLabel(this);
 
        QVBoxLayout *layout = new QVBoxLayout(central);
        layout->addWidget(label1);
        layout->addWidget(label2);
 
        central->setLayout(layout);
        setCentralWidget(central);
 
        doStuff();  // set starting labels
 
        connect(&timer, SIGNAL(timeout()), SLOT(doStuff()));
        timer.start(1000);  // actual object, use dot
    }
 
public slots:
    void doStuff() {
        static int count =  0;  // a local variable
        label1->setText( QString::number(count) );  // pointer to object, use ->
        label2->setText( QString::number(count * count) );
        ++count;
    }
 
private:
    // member variables
    QLabel *label1; // pointer to a QLabel instance
    QLabel *label2;
    QTimer timer;   // actual instance of a QTimer
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

#include <QtGui>
#include <QDebug>

class MainWindow: public QMainWindow {
    Q_OBJECT
public:
    MainWindow(QWidget *p = 0): QMainWindow(p) {
        QWidget *central = new QWidget(this);   // central is a local varaibale
        label1 = new QLabel(this);  // label1 is a member variable, a pointer to a label
        label2 = new QLabel(this);

        QVBoxLayout *layout = new QVBoxLayout(central);
        layout->addWidget(label1);
        layout->addWidget(label2);

        central->setLayout(layout);
        setCentralWidget(central);

        doStuff();  // set starting labels

        connect(&timer, SIGNAL(timeout()), SLOT(doStuff()));
        timer.start(1000);  // actual object, use dot
    }

public slots:
    void doStuff() {
        static int count =  0;  // a local variable
        label1->setText( QString::number(count) );  // pointer to object, use ->
        label2->setText( QString::number(count * count) );
        ++count;
    }

private:
    // member variables
    QLabel *label1; // pointer to a QLabel instance
    QLabel *label2;
    QTimer timer;   // actual instance of a QTimer
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    MainWindow m;
    m.show();
    return app.exec();
}
#include "main.moc"

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[ShapeShiftme]

That for the code. but all that i can do.

What i need to do is create the form dynamically but from your code you know how many input boxes are created.

In theory im might have 30 to create so i would like to loop them in creating and that i dont know how to reference them in this case.

for example i want to create 5 lineedits.

int i;
    for(i=1;i<=5;i++)
    {
       QLineEdit *myline;
       myline = new QLineEdit;
       myline->setText("Text " + QString::number(i));
       myhoz->addWidget(myline);
    }

int i;
    for(i=1;i<=5;i++)
    {
       QLineEdit *myline;
       myline = new QLineEdit;
       myline->setText("Text " + QString::number(i));
       myhoz->addWidget(myline);
    }

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now i KNOW this WONT work but this is what i want to do but i would not know how to do it.

Then what i would like to do is be able to reference the objects from another function.

Am i making myself clear at all
regards