How to correct use QtConcurrent::run



  • Hi everyone!

    In my project I need to call method which open big file, unzip content, decode using AES and parse JSON structure. In result this method should return QObject list with file structure. My problem is a problem with setParent methods for every object when I created it in other thread and I can't call signals after finish. Could you show me example how I can do this correct? Maybe I need to use something else? I've read docs about QtConcurrent::run but I can't understand best practices for use QtConcurrent::run.

    Thanks for the any help!


  • Lifetime Qt Champion

    Hi,

    Are you using the worker object technique ?



  • Hi,

    I've tried this but no luck. Maybe you have few examples how to use QtConcurrent::run and worker?



  • Hi,

    Could you help me to understand what I do wrong? I have a class to open, unzip, decode file content and then parse content to JSON object (QVariant) which I want use to create QObejcts instance. I've create a class which work only with file and create QVariant object. I want do this in separate thread. I've tried QThread and QtConcurrent but my application crashed and I can't understand why. This crash happens sometimes not every load application. Code of my function for thread looks like:

    void MdlLogParser::readLogFileContents()
    {
        if(!m_logFilePath.isEmpty())
        {
            QFile file(m_logFilePath);
            if(file.exists())
            {
                if(file.open(QIODevice::ReadOnly | QIODevice::Text))
                {
                    QTextStream stream(&file);
                    QString content = stream.readAll();
    
                    if(!content.isNull())
                    {
                        QByteArray compressedDatas = QByteArray::fromBase64(content.toUtf8());
                        QString encodedDatas = QString(uncompressDatas(compressedDatas));       //Trying to decompress source datas
                        QString decodedString;
                        if(!encodedDatas.isEmpty()) //If source datas was compressed.
                        {
                            decodedString = decode(encodedDatas, m_aesKey, m_aesIv);
                        }
                        else        //If source datas doen't compressed we trying to decode withot decompress.
                        {
                            decodedString = decode(compressedDatas, m_aesKey, m_aesIv);
                        }
    
                        //Start convert to Objects
                        if(!decodedString.isNull())
                        {
                            m_logContent = decodedString;
                            QString crashString("Crash=Y");
                            m_wasCrash = false;
                            if(m_logContent.startsWith(crashString, Qt::CaseInsensitive))
                            {
                                m_wasCrash = true;
                            }
    
                            m_logContent = QString("[") + m_logContent.mid(crashString.length(),
                                                                           m_logContent.length()-crashString.length()-1) + QString("]");
    
                            QJsonDocument doc = QJsonDocument::fromJson(m_logContent.toUtf8());
                            if(!doc.isEmpty())
                            {
                                 getDataFromJSONObject(doc.toVariant());
                            }
                            else
                            {
                                m_wasParsed = false;
                                emit wasParsedChanged(m_wasParsed);
                                m_error = new MdlLogParserError(MdlLogParserErrorCodeFileCannotBeParsed,
                                                                "The file cann't be parsed. Maybe it's not JSON data.");
                                m_error->setParent(this);
                                emit errorChanged(m_error);
                            }
                        }
                        else
                        {
                            m_error = new MdlLogParserError(MdlLogParserErrorCodeCannotBeDecoded, "Can't decode file.");
                            m_error->setParent(this);
                            emit errorChanged(m_error);
                        }
                    }
                    else
                    {
                        m_error = new MdlLogParserError(MdlLogParserErrorCodeFileIsEmpty, "The file contents is empty.");
                        m_error->setParent(this);
                        emit errorChanged(m_error);
                    }
                }
                else
                {
                    m_error = new MdlLogParserError(MdlLogParserErrorCodeFileCannotBeOpenForRead,
                                                    "The file cann't be open for read.");
                    m_error->setParent(this);
                    emit errorChanged(m_error);
                }
            }
            else
            {
                m_error = new MdlLogParserError(MdlLogParserErrorCodeFileNotFound, "The file not found.");
                m_error->setParent(this);
                emit errorChanged(m_error);
            }
        }
    }
    

    The call of method looks like:

        QtConcurrent::run(this, &MdlLogParser::readLogFileContents);
    

    The part of crash report looks like:

    Crashed Thread:        0  Dispatch queue: com.apple.main-thread
    
    Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
    Exception Codes:       EXC_I386_GPFLT
    
    Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
    0   org.qt-project.QtCore         	0x00000001096a59a3 QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) + 19
    1   org.qt-project.QtQml          	0x0000000109d4bfdc QV4::QObjectWrapper::create(QV4::ExecutionEngine*, QObject*) + 92
    2   org.qt-project.QtQml          	0x0000000109d4a976 QV4::QObjectWrapper::wrap(QV4::ExecutionEngine*, QObject*) + 950
    3   org.qt-project.QtQml          	0x0000000109d48c72 QV4::QObjectWrapper::getProperty(QObject*, QV4::ExecutionContext*, QQmlPropertyData*, bool) + 1602
    4   org.qt-project.QtQml          	0x0000000109d4841c QV4::QObjectWrapper::getQmlProperty(QV4::ExecutionContext*, QQmlContextData*, QV4::String*, QV4::QObjectWrapper::RevisionMode, bool*, bool) + 636
    5   org.qt-project.QtQml          	0x0000000109d4c266 QV4::QObjectWrapper::get(QV4::Managed*, QV4::String*, bool*) + 70
    6   org.qt-project.QtQml          	0x0000000109d57f29 QV4::Runtime::getProperty(QV4::ExecutionContext*, QV4::ValueRef, QV4::String*) + 105
    7   ???                           	0x0000000114e3c579 0 + 4645438841
    8   org.qt-project.QtQml          	0x0000000109d09190 QV4::SimpleScriptFunction::call(QV4::Managed*, QV4::CallData*) + 528
    9   org.qt-project.QtQml          	0x0000000109def45e QQmlJavaScriptExpression::evaluate(QQmlContextData*, QV4::ValueRef, QV4::CallData*, bool*) + 622
    10  org.qt-project.QtQml          	0x0000000109d96142 QQmlBoundSignalExpression::evaluate(void**) + 2258
    11  org.qt-project.QtQml          	0x0000000109d96b68 QQmlBoundSignal_callback(QQmlNotifierEndpoint*, void**) + 440
    12  org.qt-project.QtQml          	0x0000000109dd145c QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) + 92
    13  org.qt-project.QtQml          	0x0000000109d72711 QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) + 753
    14  org.qt-project.QtCore         	0x0000000109856cb7 QMetaObject::activate(QObject*, int, int, void**) + 183
    15  libqtquickcontrolsplugin.dylib	0x0000000111e1e285 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 517
    16  org.qt-project.QtCore         	0x00000001098577ab QMetaObject::activate(QObject*, int, int, void**) + 2987
    17  libqtquickcontrolsplugin.dylib	0x0000000111e1bcfd QQuickAction::triggered(QObject*) + 61
    18  libqtquickcontrolsplugin.dylib	0x0000000111e1e2a1 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 545
    19  org.qt-project.QtCore         	0x0000000109850393 QObject::event(QEvent*) + 755
    20  org.qt-project.QtWidgets      	0x000000010a21b32b QApplicationPrivate::notify_helper(QObject*, QEvent*) + 251
    21  org.qt-project.QtWidgets      	0x000000010a21e648 QApplication::notify(QObject*, QEvent*) + 8136
    22  org.qt-project.QtCore         	0x0000000109825a5b QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) + 971
    23  libqcocoa.dylib               	0x000000010d21db8e QCocoaEventDispatcherPrivate::processPostedEvents() + 190
    24  libqcocoa.dylib               	0x000000010d21e411 QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) + 33
    25  com.apple.CoreFoundation      	0x00007fff893b6681 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    26  com.apple.CoreFoundation      	0x00007fff893a880d __CFRunLoopDoSources0 + 269
    27  com.apple.CoreFoundation      	0x00007fff893a7e3f __CFRunLoopRun + 927
    28  com.apple.CoreFoundation      	0x00007fff893a7858 CFRunLoopRunSpecific + 296
    29  com.apple.HIToolbox           	0x00007fff89a47aef RunCurrentEventLoopInMode + 235
    30  com.apple.HIToolbox           	0x00007fff89a4776e ReceiveNextEventCommon + 179
    31  com.apple.HIToolbox           	0x00007fff89a476ab _BlockUntilNextEventMatchingListInModeWithFilter + 71
    32  com.apple.AppKit              	0x00007fff81d70f81 _DPSNextEvent + 964
    33  com.apple.AppKit              	0x00007fff81d70730 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 194
    34  com.apple.AppKit              	0x00007fff81d64593 -[NSApplication run] + 594
    35  libqcocoa.dylib               	0x000000010d21d2fd QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 2189
    36  org.qt-project.QtCore         	0x000000010982237d QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 381
    37  org.qt-project.QtCore         	0x000000010982535a QCoreApplication::exec() + 346
    38  com.shav.MdlViewer            	0x0000000108bde417 main + 823
    39  com.shav.MdlViewer            	0x0000000108bde0d4 start + 52
    

    Could you help me to understand what I do wrong? Thanks for the help.


  • Lifetime Qt Champion

    Just to be sure, are you connecting this to a QML UI ?



  • Yes, I'm calling this method from QML and return result to QML.


  • Lifetime Qt Champion

    Can you show how you used it both in C++ and QML ?



  • Hi,

    In QML I've called this:

        MenuItem {
            id: openLogMenuItem
            text: qsTr("Open...")
            shortcut: StandardKey.Open
    
            onTriggered: {
                if(openFileDialog !== null)
                {
                    openFileDialog.accepted.connect(function () {
                        manager.openFile(openFileDialog.fileUrl);
                        manager.viewer.settingsManager.addRecentFile(openFileDialog.fileUrl.toString());
                    });
                    openFileDialog.open();
                }
            }
        }
    

    Also I've connected slot:

    MdlManager {
        id: mdlManager
    
        onMdlLogParserDidStart: {
            spinnerView.running = true;
            cententViewLoader.setSource("");
        }
    
        onMdlLogParserDidFinished: {
            spinnerView.running = false;
            if(parser !== null)
            {
                var options = { manager: loggerInfoView.mdl};
                cententViewLoader.setSource("Components/MdlCentralWidget.qml", options);
            }
        }
    
        onMdlLogParserErrorDetected: {
            spinnerView.running = false;
        }
    }
    

    In C++ I have method:

    Q_INVOKABLE inline void openFile(QString file){m_lvManager->parseLogFile(file);}
    

    And Connected slot:

        m_lvManager = new MdlLogViewerManager();
        m_lvManager->setParent(this);
        connect(m_lvManager->getParser(), &MdlLogParser::parserDidStart, this, [this]() {
            emit mdlLogParserDidStart();
        });
        connect(m_lvManager->getParser(), &MdlLogParser::parserDidFinished, this, [this](MdlLogParser* obj) {
            emit mdlLogParserDidFinished(obj);
        });
        connect(m_lvManager->getParser(), &MdlLogParser::errorChanged, this, [this](MdlLogParserError* obj) {
            emit mdlLogParserErrorDetected(obj);
        });
        connect(m_lvManager->getSettingsManager(), &ShavSettingsManager::settingsLoaded, this, [this](bool flag, ShavSettingsManager* settings) {
            emit mdlSettingsLoaded(flag, settings);
        });
    

    And source code for method "parsingLogFile":

    void MdlLogParser::parsingLogFile(QString fPath)
    {
        try
        {
            m_wasParsed = false;
            m_logFileFolder.clear();
            m_logFilePath = fPath.replace("file://", "");
            QString logFileName = m_logFilePath.split("/").last();
            m_logFileFolder = m_logFilePath;
            m_logFileFolder.replace(logFileName, "");
    
            m_classes.clear();
            m_frameworksList.clear();
            m_sessions.clear();
            m_methods.clear();
            m_messages.clear();
            m_systemMessage.clear();
            m_images.clear();
            m_viewsStructures.clear();
    
            emit parserDidStart();
            QtConcurrent::run(this, &MdlLogParser::readLogFileContents);
        }
        catch(std::exception& exception)
        {
            ShavNotificationCenter::defaultManger()->postNotification(SHAV_NC_EXCEPTION_DETECTED, QVariant(exception.what()));
        }
    }


  • Hi, everyone!

    I still have problem with threads in my project, but now it's strange and I don't know why this happens.

    I've changed code in my project and now I have class which reading file, the content from file unzip and decoding using AES decode algorithm from QCA library. In result class generate QVariantMap object which return to main program by signal. The code of all operation looks like:

    if(!m_logFilePath.isEmpty())
    {
        m_logFilePath = m_logFilePath.replace("file://", "");
        QFile file(m_logFilePath);
        if(file.exists())
        {
            if(file.open(QIODevice::ReadOnly | QIODevice::Text))
            {
                QTextStream stream(&file);
                QString content = stream.readAll();
    
                if(!content.isNull())
                {
                    QByteArray compressedDatas = QByteArray::fromBase64(content.toUtf8());
                    QString fileContent = QString(uncompressDatas(compressedDatas));        //Trying to decompress source datas
    
                    QString decodedString;
                    if(!fileContent.isEmpty()) //If source datas was compressed.
                    {
                        decodedString = decode(fileContent, m_aesKey, m_aesIv);
                    }
                    else        //If source datas doen't compressed we trying to decode withot decompress.
                    {
                        decodedString = decode(compressedDatas, m_aesKey, m_aesIv);
                    }
    
                    //Start convert to Objects
                    if(!decodedString.isNull())
                    {
                        QString crashString("Crash=Y");
                        bool wasCrash = false;
                        if(decodedString.startsWith(crashString, Qt::CaseInsensitive))
                        {
                            wasCrash = true;
                        }
    
                        decodedString = QString("[") + decodedString.mid(crashString.length(),
                                                                         decodedString.length()-crashString.length()-1) + QString("]");
    
                        QJsonDocument doc = QJsonDocument::fromJson(decodedString.toUtf8());
                        if(!doc.isEmpty())
                        {
                            QVariant data = doc.toVariant();
                            QList<QVariant> list = data.toList();
    
                            if(!list.isEmpty())
                            {
                                QVariantMap jsonObj, crashImage, startSession;
                                QVariantList methods, viewsList, classes, messageList, systemsList, frameworks, images, loggerMessagesList, loggerExceptionsList, sessions;
    
                                foreach(QVariant item, list)
                                {
                                    QVariantMap obj = item.toMap();
                                    QString componentType = obj.value(QString("componentType")).toString();
                                    QString action = obj.value(QString("action")).toString();
    
                                    if(componentType == QString("DeviceInfo"))
                                    {
                                        jsonObj["deviceInfo"] = obj;
                                    }
                                    else if(componentType == QString("ApplicationInfo"))
                                    {
                                        jsonObj["appInfo"] = obj;
                                    }
                                    else if(componentType == QString("LoggerInfo"))
                                    {
                                        jsonObj["loggerInfo"] = obj;
                                    }
                                    else if(componentType == QString("Crash"))
                                    {
                                        jsonObj["crashLog"] = obj;
                                    }
                                    else if(componentType == QString("StatisticObject"))
                                    {
                                        jsonObj["statistic"] = obj;
                                    }
                                    else if(componentType == QString("Method"))
                                    {
                                        methods.append(obj);
                                    }
                                    else if(componentType == QString("LibImages"))
                                    {
                                        frameworks = obj["list"].toList();
                                    }
                                    else if(componentType == QString("Image"))
                                    {
                                        images.append(obj);
    
                                        bool isCrash = obj["forCrash"].toBool();
                                        if(isCrash)
                                        {
                                            crashImage = obj;
                                        }
                                    }
                                    else if(componentType == QString("ViewStructure"))
                                    {
                                        viewsList.append(obj);
                                    }
                                    else if(componentType == QString("LoggerMessage"))
                                    {
                                        if(action == QString("Exception"))
                                        {
                                            loggerExceptionsList.append(obj);
                                        }
                                        else
                                        {
                                            loggerMessagesList.append(obj);
                                        }
                                    }
                                    else if(componentType == QString("Message"))
                                    {
                                        messageList.append(obj);
                                    }
                                    else if(componentType == QString("SystemMessage"))
                                    {
                                        systemsList.append(obj);
                                    }
                                    else if(componentType == QString("Class"))
                                    {
                                        classes.append(obj);
                                    }
                                    else if(componentType == QString("Session"))
                                    {
                                        if(action == QString("SessionStart"))
                                        {
                                            startSession = obj;
                                        }
                                        else if(action == QString("SessionFinished"))
                                        {
                                            QVariantMap map = startSession;
                                            map["start"] = startSession["timestamp"];
                                            map["end"] = obj["timestamp"];
                                            map["length"] = (obj["timestamp"].toDouble() - startSession["timestamp"].toDouble());
                                            sessions.append(map);
                                        }
                                    }
                                }
    
    
                                QString path = m_logFilePath;
                                QString logFile = m_logFilePath.split("/").last();
                                QString logFileFolder = path.replace(logFile, "");
    
                                jsonObj["logFilePath"] = m_logFilePath;
                                jsonObj["logFileFolder"] = logFileFolder;
                                jsonObj["logContent"] = decodedString;
                                jsonObj["wasCrash"] = wasCrash;
    
                                jsonObj["classes"] = classes;
                                jsonObj["methods"] = methods;
                                jsonObj["viewsStructures"] = viewsList;
                                jsonObj["messages"] = messageList;
                                jsonObj["systemMessage"] = systemsList;
                                jsonObj["frameworksList"] = frameworks;
                                jsonObj["images"] = images;
                                jsonObj["sessions"] = sessions;
    
                                QVariantMap crashLog = jsonObj["crashLog"].toMap();
                                crashLog["image"] = crashImage;
                                jsonObj["crashLog"] = crashLog;
    
                                QVariantMap loggerInfo = jsonObj["loggerInfo"].toMap();
                                loggerInfo["messages"] = loggerMessagesList;
                                loggerInfo["exceptions"] = loggerExceptionsList;
                                jsonObj["loggerInfo"] = loggerInfo;
    
                                emit fileReaderDidFinish(jsonObj);
                            }
                        }
                    }
                }
            }
        }
    }
    
    emit fileReaderDidFinish(QVariant());
    

    When I need to use class I've called this code:

        if(!file.isEmpty())
        {
            emit m_parser->parserDidStart();
    
            QThread* thread = new QThread(this);
            MdlFileReader* fileReader = new MdlFileReader(file, m_settingsManager->getAesKey(), m_settingsManager->getAesInventoryKey());
            fileReader->moveToThread(thread);
            connect(fileReader, &MdlFileReader::fileReaderDidFinish, this, [this, file](QVariant jsonObj) {
    
                if(!jsonObj.isNull())
                {
                    m_parser->updateFromJSONObject(jsonObj);
                }
            }, Qt::QueuedConnection);
            connect(thread, &QThread::started, fileReader, &MdlFileReader::startParseFile);
            thread->start();
        }
    

    The problem is sometimes this code works and application does't crash. But sometimes application crashes. It's could happens every second time when I load application (without rebuild).

    I've also tried QtConcurrent::run but no luck.

    Full crash report looks like:

    Process:               MdlViewer [6460]
    Path:                  /Volumes/VOLUME/*/MdlViewer.app/Contents/MacOS/MdlViewer
    Identifier:            com.shav.MdlViewer
    Version:               1.0.0 (1.0.0)
    Code Type:             X86-64 (Native)
    Parent Process:        Qt Creator [6229]
    Responsible:           Qt Creator [6229]
    User ID:               501
    
    Date/Time:             2015-03-13 20:35:02.729 +0200
    OS Version:            Mac OS X 10.10.2 (14C1510)
    Report Version:        11
    Anonymous UUID:        01BBAAA2-2A09-5EF9-08B9-47ED5259279D
    
    
    Time Awake Since Boot: 39000 seconds
    
    Crashed Thread:        0  Dispatch queue: com.apple.main-thread
    
    Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
    Exception Codes:       EXC_I386_GPFLT
    
    Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
    0   org.qt-project.QtQml          	0x000000010795c5ea QV4::QObjectWrapper::wrap(QV4::ExecutionEngine*, QObject*) + 42
    1   org.qt-project.QtQml          	0x000000010795ac72 QV4::QObjectWrapper::getProperty(QObject*, QV4::ExecutionContext*, QQmlPropertyData*, bool) + 1602
    2   org.qt-project.QtQml          	0x000000010795a41c QV4::QObjectWrapper::getQmlProperty(QV4::ExecutionContext*, QQmlContextData*, QV4::String*, QV4::QObjectWrapper::RevisionMode, bool*, bool) + 636
    3   org.qt-project.QtQml          	0x000000010795e266 QV4::QObjectWrapper::get(QV4::Managed*, QV4::String*, bool*) + 70
    4   org.qt-project.QtQml          	0x0000000107969f29 QV4::Runtime::getProperty(QV4::ExecutionContext*, QV4::ValueRef, QV4::String*) + 105
    5   ???                           	0x0000000112f7c9b9 0 + 4613196217
    6   org.qt-project.QtQml          	0x000000010791b190 QV4::SimpleScriptFunction::call(QV4::Managed*, QV4::CallData*) + 528
    7   org.qt-project.QtQml          	0x0000000107a0145e QQmlJavaScriptExpression::evaluate(QQmlContextData*, QV4::ValueRef, QV4::CallData*, bool*) + 622
    8   org.qt-project.QtQml          	0x00000001079a8142 QQmlBoundSignalExpression::evaluate(void**) + 2258
    9   org.qt-project.QtQml          	0x00000001079a8b68 QQmlBoundSignal_callback(QQmlNotifierEndpoint*, void**) + 440
    10  org.qt-project.QtQml          	0x00000001079e345c QQmlNotifier::emitNotify(QQmlNotifierEndpoint*, void**) + 92
    11  org.qt-project.QtQml          	0x0000000107984711 QQmlData::signalEmitted(QAbstractDeclarativeData*, QObject*, int, void**) + 753
    12  org.qt-project.QtCore         	0x0000000107467cb7 QMetaObject::activate(QObject*, int, int, void**) + 183
    13  libqtquickcontrolsplugin.dylib	0x000000010fe15285 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 517
    14  org.qt-project.QtCore         	0x00000001074687ab QMetaObject::activate(QObject*, int, int, void**) + 2987
    15  libqtquickcontrolsplugin.dylib	0x000000010fe12cfd QQuickAction::triggered(QObject*) + 61
    16  libqtquickcontrolsplugin.dylib	0x000000010fe152a1 QQuickMenuItem::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) + 545
    17  org.qt-project.QtCore         	0x0000000107461393 QObject::event(QEvent*) + 755
    18  org.qt-project.QtWidgets      	0x0000000107e2632b QApplicationPrivate::notify_helper(QObject*, QEvent*) + 251
    19  org.qt-project.QtWidgets      	0x0000000107e29648 QApplication::notify(QObject*, QEvent*) + 8136
    20  org.qt-project.QtCore         	0x0000000107436a5b QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) + 971
    21  libqcocoa.dylib               	0x000000010aea0b8e QCocoaEventDispatcherPrivate::processPostedEvents() + 190
    22  libqcocoa.dylib               	0x000000010aea1411 QCocoaEventDispatcherPrivate::postedEventsSourceCallback(void*) + 33
    23  com.apple.CoreFoundation      	0x00007fff8f285681 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    24  com.apple.CoreFoundation      	0x00007fff8f27780d __CFRunLoopDoSources0 + 269
    25  com.apple.CoreFoundation      	0x00007fff8f276e3f __CFRunLoopRun + 927
    26  com.apple.CoreFoundation      	0x00007fff8f276858 CFRunLoopRunSpecific + 296
    27  com.apple.HIToolbox           	0x00007fff8e010aef RunCurrentEventLoopInMode + 235
    28  com.apple.HIToolbox           	0x00007fff8e01076e ReceiveNextEventCommon + 179
    29  com.apple.HIToolbox           	0x00007fff8e0106ab _BlockUntilNextEventMatchingListInModeWithFilter + 71
    30  com.apple.AppKit              	0x00007fff8c903f81 _DPSNextEvent + 964
    31  com.apple.AppKit              	0x00007fff8c903730 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 194
    32  com.apple.AppKit              	0x00007fff8c8f7593 -[NSApplication run] + 594
    33  libqcocoa.dylib               	0x000000010aea02fd QCocoaEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 2189
    34  org.qt-project.QtCore         	0x000000010743337d QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 381
    35  org.qt-project.QtCore         	0x000000010743635a QCoreApplication::exec() + 346
    36  com.shav.MdlViewer            	0x00000001067ebe57 main + 663
    37  com.shav.MdlViewer            	0x00000001067ebbb4 start + 52
    

    What I do wrong? Thanks for the any help!



  • @shav Where is objects deletion?

    http://doc.qt.io/qt-5/qthread.html Documentation contains very useful examles



  • @jalomic Thanks for the reply!

    I've added the attribute to my main class which must separate thread as

        /** Thread for read file.*/
        QThread* m_thread;
    

    In constructor of my class I've aded this line to create thread instance like this:

        m_thread = new QThread(this);
    

    and method where I'm using this thread looks like this:

            MdlFileReader* fileReader = new MdlFileReader(file, m_settingsManager->getAesKey(), m_settingsManager->getAesInventoryKey());
            fileReader->moveToThread(m_thread);
            connect(fileReader, &MdlFileReader::fileReaderDidFinish, this, [this](QVariant jsonObj) {
    
                m_thread->quit();
                m_thread->wait();
    
                if(!jsonObj.isNull())
                {
                    m_parser->updateFromJSONObject(jsonObj);
                }
            });
    
            connect(m_thread, &QThread::started, fileReader, &MdlFileReader::startParseFile);
            m_thread->start();
    

    in destructor of my main class I've added this line:

        m_thread->deleteLater();
    

    By the way how I can call slot from main thread if signal send from separate thread? Maybe problem is that I'm updating GUI in separate thread? Because in QML I have slot which uses Loader to load QML file. This slot called when file was parse and ready to use.


  • Lifetime Qt Champion

    The connection should be queued, so the slot will be executed in the receiver thread (hence the use of signals and slots to transmit information for the GUI part to update)

    I wonder if your object gets garbage collected



  • Thanks! But I've tried this and this didn't help me to solved problem :-(

    About GC I'll check.



  • @shav connect(m_thread, &QThread::finished, fileReader, &QObject::deleteLater);



  • @jalomic Thanks I'll try this.


  • Lifetime Qt Champion

    About the ownership: here is the doc



  • @SGaist Thanks for the link! I'll check it!


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