Need help connecting signal from thread to slot in GUI - qt

Question

mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void disableStartButton();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
myobject.h
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <QtCore>
class MyObject : public QObject
{
Q_OBJECT
public:
explicit MyObject(QObject *parent = 0);
void doSetup(QThread &cThread);
signals:
void disableStartButton();
public slots:
void doWork();
};
#endif // MYOBJECT_H
main.cpp:
#include "mainwindow.h"
#include "myobject.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
QThread cThread;
MyObject cObject;
cObject.doSetup(cThread);
cObject.moveToThread(&cThread);
return a.exec();
}
mainwindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::disableStartButton() {
ui->pushButton->setEnabled(false);
}
myobject.h:
#include "myobject.h"
#include <QDebug>
MyObject::MyObject(QObject *parent) :
QObject(parent)
{
}
void MyObject::doSetup(QThread &cThread)
{
connect(&cThread, SIGNAL(started()), this, SLOT(doWork()));
connect(ui->pushButton, SIGNAL(clicked()), &cThread, SLOT(start())); // (1)
connect(this, SIGNAL(disableStartButton()), ui, SLOT(disableStartButton())); // (2)
}
void MyObject::doWork()
{
emit disableStartButton();
qDebug() << "1";
}
I'm trying to do two things.
(1): As soon pushButton is clicked, I want cThread to start.
(2): As soon as cThread starts, it does: emit disableStartButton();. I want to connect disableStartButton() to disableStartButton() in mainwindow.cpp.
For (1), I get this error:
myobject.cpp:12: error: C2065: 'ui' : undeclared identifier

Answer 1

Of course, there ui is undefined. You try to connect ui->pushButton
connect(ui->pushButton, SIGNAL(clicked()), &cThread, SLOT(start())); // (1)
in file myobject.cpp, when your ui declared only in mainwindow.cpp
You have to connect pushbutton to your thread within mainwindow.cpp file, hope that helps
By the way, you should create your objects NOT in main.cpp but, in your case, in mainwindow.cpp, move lines
QThread cThread;
MyObject cObject;
cObject.doSetup(cThread);
cObject.moveToThread(&cThread);
to file mainwindow.cpp in constructor, for example
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
right after ui->setupUi(this);