We deserve something better than an untitled task. The user needs to define its name when it's created. The easiest path would be to display a dialog where the user can input the task name. Fortunately Qt offers us a very configurable dialog that fits perfectly in addTask():

#include <QInputDialog> 
... 
void MainWindow::addTask() 
{ 
    bool ok; 
    QString name = QInputDialog::getText(this,  
        tr("Add task"), 
        tr("Task name"), 
        QLineEdit::Normal, 
        tr("Untitled task"),               &ok); 
    if (ok && !name.isEmpty()) { 
        qDebug() << "Adding new task"; 
        Task* task = new Task(name); 
        mTasks.append(task); 
        ui->tasksLayout->addWidget(task); 
    } 
} 

The QinputDialog::getText function is a static blocking function that displays the dialog. When the user validates/cancels the dialog, the code continues. If we run the application and try to add a new task, we'll see this:

The QInputDialog::getText signature looks like this:

QString QinputDialog::getText( 
  QWidget* parent,  
      const QString& title,  
      const QString& label,  
      QLineEdit::EchoMode mode = QLineEdit::Normal,  
      const QString& text = QString(),  
      bool* ok = 0, ...)

Let's break it down:

There are a few more optional parameters we can safely ignore for our example.