Hi,

Why I see: Object::connect: No such slot QDialog::showName(QString) in ../DialogByButton/mainwindow.cpp:29

DialogByButton.pro
Qt Code: 
  1. SOURCES += \
  2.     main.cpp \
  3.     mainwindow.cpp \
  4.     dialog.cpp
  5.  
  6. HEADERS += \
  7.     mainwindow.h \
  8.     dialog.h
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dialog.h
Qt Code: 
  1. #ifndef DIALOG_H
  2. #define DIALOG_H
  3.  
  4. #include <QDialog>
  5. #include <QtGui>
  6.  
  7. class Dialog : public QDialog
  8. {
  9.     Q_OBJECT
  10. public:
  11.     explicit Dialog(QWidget *parent = 0);
  12.  
  13. signals:
  14.  
  15. public slots:
  16.     void showName(QString name);
  17.  
  18. private:
  19.     QLabel *lblName;
  20. };
  21.  
  22. #endif // DIALOG_H
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dialog.cpp
Qt Code: 
  1. #include "dialog.h"
  2.  
  3. Dialog::Dialog(QWidget *parent) :
  4.     QDialog(parent)
  5. {
  6.     // Controls
  7.     lblName = new QLabel(tr("Hahah"));
  8.  
  9.     // Layouts
  10.     QHBoxLayout* mainLayout = new QHBoxLayout(this);
  11.     mainLayout->addWidget(lblName);
  12.  
  13.     // Set Layout
  14.     this->setLayout(mainLayout);
  15. }
  16.  
  17. void Dialog::showName(QString name) {
  18.     //lblName->setText(name);
  19. }
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mainwindow.h
Qt Code: 
  1. #ifndef MAINWINDOW_H
  2. #define MAINWINDOW_H
  3.  
  4. #include <QMainWindow>
  5. #include <QtGui>
  6.  
  7. class MainWindow : public QMainWindow
  8. {
  9.     Q_OBJECT
  10. public:
  11.     explicit MainWindow(QWidget *parent = 0);
  12.  
  13. signals:
  14.     void sendName(QString name);
  15.  
  16. private slots:
  17.     void callDialog();
  18.  
  19. private:
  20.     QLineEdit *leName;
  21. };
  22.  
  23. #endif // MAINWINDOW_H
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mainwindow.cpp
Qt Code: 
  1. #include "mainwindow.h"
  2. #include "dialog.h"
  3. #include <QWidget>
  4.  
  5. MainWindow::MainWindow(QWidget *parent) :
  6.     QMainWindow(parent)
  7. {
  8.     // Controls
  9.     QLabel *lblName = new QLabel(tr("Enter your name:"));
  10.     leName = new QLineEdit;
  11.     QPushButton *btnCallDialog = new QPushButton(tr("Call Dialog"));
  12.  
  13.     // Layout
  14.     QGridLayout *mainLayout = new QGridLayout;
  15.     mainLayout->addWidget(lblName, 0, 0);
  16.     mainLayout->addWidget(leName, 0, 1);
  17.     mainLayout->addWidget(btnCallDialog, 1, 0, 1, 2);
  18.  
  19.     // Set center widget
  20.     QWidget *widget = new QWidget;
  21.     widget->setLayout(mainLayout);
  22.     this->setCentralWidget(widget);
  23.  
  24.     connect(btnCallDialog, SIGNAL(clicked()), this, SLOT(callDialog()));
  25. }
  26.  
  27. void MainWindow::callDialog() {
  28.     QDialog *dialog = new QDialog(this);
  29.     connect(this, SIGNAL(sendName(QString)), dialog, SLOT(showName(QString)));
  30.     emit sendName(leName->text());
  31.     dialog->show();
  32. }
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main.cpp
Qt Code: 
  1. #include <QApplication>
  2. #include "mainwindow.h"
  3.  
  4. int main (int argc, char *argv[]) {
  5.     QApplication app(argc, argv);
  6.  
  7.     MainWindow window;
  8.     window.show();
  9.  
  10.     return app.exec();
  11. }
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Thank you!