How to Connect Signal from MainWindow to Slot in Dialog - c++

Question

I have signal in my MainWindow to emit a number thats in a line edit. When I click a button to open the dialog, I want that number to be copied to the line edit in the dialog. I can't get it to connect. I can see the signal is emitting with qDebug. Am I connecting it wrong or in the wrong place? I have tried many ways. Here are my code snippets.
Mainwindow
//My MainWindow
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) {
ui->setupUi(this);
//This is the number I am trying to send to the dialog
ui->checkingAmount->setText(QString::number(1000.00, 'f', 2));
ui->checkingAmount->setReadOnly(true);
}
//Emit the data here
void MainWindow::on_transferButton_clicked() {
transferWindow = new TransferWindow(this);
transferWindow->show();
//trying to emit the data
QString data =ui->checkingAmount->text();
emit shareCheckingData(data);
qDebug()<<"emitting mainwin amount";
}
Dialog
//My Dialog
TransferWindow::TransferWindow(QWidget *parent) : QDialog(parent),ui(new Ui::TransferWindow) {
ui->setupUi(this);
//I have tried several variations of this
//mainWindow = new MainWindow();
connect(mainWindow, SIGNAL(shareCheckingData(QString)),this, SLOT(getAmountFromMainWin(QString)));
}
//Here is the connecting slot to get the data from main window
void TransferWindow::getAmountFromMainWin(QString n) {
float CheckTotal = n.toFloat();
ui->checkingAmount->setReadOnly(true);
ui->checkingAmount->setText(QString::number(CheckTotal));
qDebug()<<"setting amount";
}
How can I get this to connect? I read through many posts and it did not solve the problem. Thanks.

Answer 1

I notice in the comments of your code that you intend to create an instance of MainWindow and try to connect to this instance, that is a new instance different from the previous one so you will not be able to get it.
First we must create the instance and then connect it, that we can do in the constructor.
MainWindow.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
ui->checkingAmount->setText(QString::number(1000.00, 'f', 2));
ui->checkingAmount->setReadOnly(true);
transferWindow = new TransferWindow(this);
connect(this, &MainWindow::shareCheckingData, transferWindow, &TransferWindow::getAmountFromMainWin);
//old style
//connect(this, SIGNAL(shareCheckingData(QString)), transferWindow, SLOT(getAmountFromMainWin(QString)));
}
void MainWindow::on_transferButton_clicked()
{
//trying to emit the data
QString data =ui->checkingAmount->text();
emit shareCheckingData(data);
qDebug()<<"emitting mainwin amount";
transferWindow->show();
}
TransferWindow.cpp
TransferWindow::TransferWindow(QWidget *parent) :
QDialog(parent),
ui(new Ui::TransferWindow)
{
ui->setupUi(this);
}
void TransferWindow::getAmountFromMainWin(QString n)
{
float CheckTotal = n.toFloat();
ui->checkingAmount->setReadOnly(true);
ui->checkingAmount->setText(QString::number(CheckTotal));
qDebug()<<"setting amount";
}