how to access a widget from another class - qt

Question

I have two classes(MyWidget,ViewContact). In MyWidget, there is a QLineEdit and QListWidget. The contents in the QListWidget changes dynamically while changes in QLineEditt.
In ViewContact class there is many widgets.The ViewContact class is called by MyWidget class.
void MyWidget::viewbind(QListWidgetItem *item)
{
LblNames *widget = (LblNames*)( listWidget->itemWidget(item) );
ViewContacts *v=new ViewContacts(widget->getLabelId());
v->show();
}
then ViewContact widget shown as a window,no problem.works fine.
while clicking an update button inside ViewContact class i need to close that window and change the text inside MyWidget .now i just close the ViewContact by this.close(); function.
I give QLineEdit as public and try to change the text. No errors occur. But no changes display in QLineEdit inside MyWidget

Answer 1

Add a signal in the ViewContact class and emit a signal while close ViewContact Widget.The signal should contain a string to bind your list view.Before initiating ViewContact Widget from MyWidget ,should connect the signal and setText(const QString) slot.

Answer 2

Add the MyWidget as a parent to your ViewContacts instance. This will allow you to call a function to update the text (and it will also fix the memory leak which you currently have in your code).
You need a constructor for your ViewContacts that takes both a parent and the labelId.
class ViewContacts : public QWidget // or whatever it is, you didn't tell
{
Q_OBJECT
public:
// I don't know the class of "LabelId" either
explicit ViewContacts(LabelId id, QObject* parent = 0) : QWidget(parent)
{
// ...
}
void updateTextInParent()
{
MyWidget* w = qobject_cast<MyWidget*>(this->parent());
if (NULL != w)
{
// w is a valid pointer to a MyWidget instance
// you can access any public fields and function through it.
}
}
};
You should also use qobject_cast or dynamic_cast in the snippet you provided because a blind cast is not safe.

Answer 3

This seems like a perfect time to take advantage of Qt's signals and slots. You can connect a signal that emits the value you want to update in your MyWidget object, from your ViewContacts widget.
First you'll need to create a signal that emits the changed value when the ViewContacts widget is closed.
Something like:
Q_SIGNALS:
void value_changed_signal( QString value );
Next you'll want to add a slot, it can be private, in your MyWidget parent class
The declaration would look something like:
private Q_SLOTS:
void update_text( QString value );
Finally, in your MyWidget class, somewhere after you have instantiated your ViewContacts object, connect the signal and slot with something like:
connect(new_view_contacts_object, SIGNAL( value_changed_signal( QString ) ),
this, SLOT( update_text( QString ) ) );