QThread demo

main.cpp

#include <QtWidgets>
#include <QThread>
#include <QObject>
#include <QApplication>
#include <QWidget>
#include <QVBoxLayout>
#include <QTextEdit>


 class Thread : public QThread
{
    Q_OBJECT
 public:
    Thread(QObject* parent) : QThread(parent) {}
 protected:
    void run() override {
        /* Long running operation */
        Thread::sleep(3);
        emit result("I <3 thread");
    }
 signals:
    void result(const QString& data);
};

 int main(int argc, char* argv[]){
     QApplication a(argc, argv);

     /* Simple UI*/
     auto widget = new QWidget();
     auto vLayout = new QVBoxLayout(widget);
     auto textEdit = new QTextEdit(widget);
     vLayout->addWidget(textEdit);
     vLayout->addWidget(new QPushButton("click me to test blocking UI", widget));

     /* Setup thread */
     auto work_thread = new Thread();
     QObject::connect(work_thread, &Thread::result, textEdit, &QTextEdit::append); 
     QObject::connect(work_thread, &Thread::finished, work_thread, &QObject::deleteLater); 
     work_thread->start();

     widget->show();

     return a.exec();
}

 /* If define class QT in cpp file, have to add this include to bypass build error */
 /* https://stackoverflow.com/a/41844844 */
#include "main.moc"

thread-demo.pro

#-------------------------------------------------
#
# Project created by QtCreator 2019-06-17T22:08:10
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = thread-demo
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0


SOURCES += main.cpp