Qt/C++ - Lesson 047. QThread – How to make threads in Qt

Qt, QThread, потоки

One of the most common ways to create a separate parallel threads in an application to Qt , and perform useful tasks in them is the inheritance of QThread class and override the method run() , which will be carried out and useful application code. When meeting with threads have read different opinions on this subject, and in this lesson will get acquainted with one of the possible ways to work with streams, but which are not considered to be the best option.

In general, if we make the class inherit from the QThread , it is logical to assume that this is done with the intention that it is not sufficient functionality of the class. But when this is done only with the aim to bring in, which must be performed in a separate thread run() method a useful code, then there is clearly something wrong. In addition, de might be a problem with scaling applications and reuse code, particularly hard this can be shown in the case where such inherited class becomes quite a lot.

This method is the low level, and is used primarily for customization native streams. What is somewhat contrary to the usual need to complete a task in a separate thread. That is, as mentioned above, such an approach is primarily needed to extend the functionality class. Nevertheless, this method is necessary to consider what and proceed.


This example is very small, so we will not go into the details of the project structure. Note that there will be created a console application in the file main.cpp which will create three streams with different names. A stream classes will be inherited from QThread .

#include <QCoreApplication>
#include "examplethreads.h"

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

    ExampleThreads threadA("thread A"); 
    ExampleThreads threadB("thread B"); 
    ExampleThreads threadC("thread C");

    threadA.start();    // Run threads
    threadB.start();    // and seeing their parallel operation
    threadC.start();    // in the output qDebug

    return a.exec();



#include <QThread>

class ExampleThreads : public QThread
    explicit ExampleThreads(QString threadName);

    // Override run () method, which will be located 
    // executable code
    void run();
    QString name;   // thread name



#include "examplethreads.h"
#include <QDebug>

ExampleThreads::ExampleThreads(QString threadName) :


void ExampleThreads::run()
    for (int i = 0; i <= 100; i++ ) {
        qDebug() << name << " " << i;

Output threads


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June 24, 2019, 10:23 a.m.
Евгений Легоцкой

Хорошо, ну будут проблемы помимо того, что касается статей, то не стесняйтесь задавать вопросы на форуме.
June 24, 2019, 10:21 a.m.
Михаил Булатов

Извиняюсь, все работает(из-за невнимательности).
June 24, 2019, 9:52 a.m.
Евгений Легоцкой

Придётся делать ещё сигнал в дочернем qml и пробрасывать через коннекты и обработчики. А вообще нужно смотреть конкретный код и что вы пытаетесь сделать. Так что лучше будет, если вы зад...
June 21, 2019, 8:31 a.m.
Ruslan Polupan

Вот моя строка по которой все отлично сработало %cqtdeployer% -bin c:/CentralMposKeys/CentalMposKeys.exe -qmake c:/Qt/5.12.2/mingw73_64/bin/qmake.exe
June 21, 2019, 8:24 a.m.
Андрей Янкович

Возможно кому то пригодится сqtdeployer для windows работает точно так же как и для Linux разница лишь в команде запуска Linux: cqtdeployer Windows: %cqtdeployer...
Now discuss on the forum
June 25, 2019, 6:16 p.m.
Алексей Внуков

только через webengine, прямого апи у Яндекса нет, вроде что-то есть у гугла, сам только начал интересоваться этим вопросом
June 25, 2019, 5:05 p.m.

Само заработало. Странно.
June 25, 2019, 2:32 p.m.

Похоже глюк вебсокета. К другим вебсокетам подключаюсь.
June 25, 2019, 1:55 p.m.
Андрей Янкович

падало потому что boolStatus был на стеке метода, после завершения метода переменная убивалась, и на обращении к ней было падение.просто сделай вот так: connect(&t, &QTimer::timeou...
June 25, 2019, 10:55 a.m.

По пункту 3 попытался переписать метод setData. В итоге комбобокс перестал работать. bool MySqlTableModel::setData(const QModelIndex& index, const QVariant& value, int /* role */){...
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