Qt sending data from parent to child widget

Question

I have a 2 widgets inherited from QDialog. One of these widgets is called by another widget.

I need to pass data from the parent widget to the child. For example, I want passing QStringList.

I can make signals and slots in both classes. Slot of parent widget class - transferList(QStringList) - filling my QStringList.

How should I make the signal and slot connection? The child widget, of course, knows nothing about the parent.

// .h-file of parent widget. 
class ElectricIndicationDialog : public QDialog {

#include "PollIndication.h" // class of child widget
QSharedPointer <PollIndication> pollInd;

public slots:
    void transferList(QStringList);
signals:
    void listTfansfer(QStringList);
private:
    QStringList sendList;
};


// .cpp-file of parent widget
pollInd = QSharedPointer <PollIndication>(new PollIndication());
pollInd->show();

void ConfIndication::transferList(QStringList lst) {
    lst.append("str1");
    lst.append("str2");
}


// .h-file of child widget
class PollIndication : public QDialog {
public slots:
    void getList(QStringList);
signals:
    void listGet(QStringList);
private:
    QStringList recList; // We transfer data to it
}

Dimitry Ernot Dimitry Ernot · Accepted Answer · 2019-02-04T10:41:45

You don't need a signal/slot for that: your parent knows the type of its child and has a pointer on it. So, you can call a method of PollIndication when you need to send data to your dialog.

void ConfIndication::transferList(QStringList lst) {
    lst.append("str1");
    lst.append("str2");
    pollInd->changeTransferList(lst);
}

If your dialog is modal, you can also create your dialog only when needed and give your list as parameter of the constructor.

void ConfIndication::transferList(QStringList lst) {
    lst.append("str1");
    lst.append("str2");
    PollIndication* pollInd = new PollIndication(lst, this);
    pollInd->exec();
}

Qt sending data from parent to child widget

2 Answers