Qt: Change MainWindow Label Text By Click From Dialog

Question

Case: App starts, MainWindow opens, then auto-show dialog window (call this A). There's a button in A called 'btn'. In MainWindow, I have a label called 'sometext_label'. What I want is, when 'btn' is clicked, change 'sometext_label' text to "Hi!" for example, and then close dialog A. When dialog A is closed, the label's text should already be changed to "Hi!".

I have written my code and it's trash. It doesn't work. So, how you do it? I've tried using connect function, the signal and slot, but it's not changing anything..

//MainWindow.h
...
private slots:
    void Get();
...

//MainWindow.cpp
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    A = new DialogA; //DialogA *A in MainWindow.h
    connect(A, SIGNAL(Send()), this, SLOT(Get()));
}

void MainWindow::Get(){
    ui->Sometext_label->setText("Hi!");
}

//DialogA.h
...
signals:
    void Send();
...

//DialogA.cpp
void DialogA::on_btn_clicked()
{
    emit Send();
}

Solution: In my case, I use dialog.exec() function to call the dialog window. Instead, just use dialog.show() function or it won't do good...