[SOLVED]Cann't create signals ?



  • Dear Qt Forumers, I wrote simple programm to learn more about threads ssynchronization and have encountered problem when tried to build executable. The compiler couldn't find reference to one of signals SetMyText(QString, int). Could you please be so kind to help me with this bug (I waste enough time and exhausted). Thank you for help in advance. Please, take a look on codes:
    main.cpp
    @
    #include <QApplication>
    #include "ThreadAB.h"
    #include "MyThread.h"
    #include "MyString.h"
    int main(int argc, char *argv[]){

    QApplication a(argc, argv);
    //    QDebugStream cerr(std::cerr);
    //    QDebugStream cout(std::cout);
    
    ThreadAB *window = new  ThreadAB();
    window -> show();
    
    return a.exec&#40;&#41;;
    

    }
    @

    MyThread.h

    @
    #ifndef MYTHREAD_H
    #define MYTHREAD_H
    #include <QApplication>
    #include <QThread>
    class Thread : public QThread
    {
    public:
    Thread();

    void run();
    void stop();
    void setThreadName(QString);
    QString thread_name;
    int running_number;

    private:
    volatile bool stopped;

    signals:
    void SetMyText (QString, int);
    };
    #endif //MYTHREAD_H
    @

    MyThread.cpp

    @
    #include "MyThread.h"
    #include <QDebug>
    Thread::Thread()
    {
    stopped = false;
    }
    void Thread::run()
    {
    while (!stopped) {
    running_number += 1;
    if(thread_name.left(1) == "A")
    qDebug() << thread_name << ": running_number= " << running_number << endl;
    else
    qDebug() << " "
    << thread_name << ": running_number= " << running_number << endl;

      sleep(1);
    

    }
    emit SetMyText(thread_name, running_number);
    // stopped = false;
    }
    void Thread::stop()
    {
    stopped = true;
    }
    void Thread::setThreadName(QString message)
    {
    thread_name = message;
    running_number = 0;
    }
    @

    ThreadAB.h

    @
    #ifndef THREADAB_H
    #define THREADAB_H
    #include "MyThread.h"
    #include "QDialog"
    #include <QCloseEvent>
    class ThreadAB : public QDialog
    {
    Q_OBJECT

    public: 
    

    ThreadAB(QWidget *parent = 0);

    protected:
    void closeEvent(QCloseEvent *event);

    private:
    Thread *threadA;
    Thread *threadB;
    QPushButton *threadAButton;
    QPushButton *threadBButton;
    QPushButton *quitButton;

    private slots:
    void startOrStopThreadA();
    void startOrStopThreadB();

    };
    #endif //THREADAB_H
    @

    ThreadAB.cpp

    @
    #include "ThreadAB.h"
    #include "MyString.h"
    #include <QTextCodec>
    #include <QPushButton>
    #include <QHBoxLayout>
    ThreadAB::ThreadAB(QWidget *parent)
    : QDialog(parent)
    {
    QTextCodec *utfcodec = QTextCodec::codecForName("UTF-8");
    QTextCodec::setCodecForTr(utfcodec);
    QTextCodec::setCodecForCStrings(utfcodec);

    this->setWindowTitle("Threads");
    threadA = new Thread();
    threadB = new Thread();

    threadA -> setThreadName("A thread");
    threadB -> setThreadName("B thread");
    // threadA -> running_number=0;
    // threadB -> running_number=0;
    threadAButton = new QPushButton(tr("Start A"), this);
    threadBButton = new QPushButton(tr("Start B"), this);
    quitButton = new QPushButton(tr("Quit"), this);
    quitButton -> setDefault(true);
    // layout : start
    QHBoxLayout *layout = new QHBoxLayout;
    layout -> addWidget(threadAButton);
    layout -> addWidget(threadBButton);
    layout -> addWidget(quitButton);
    this -> setLayout(layout);

    connect(threadAButton, SIGNAL(clicked()),
    this, SLOT(startOrStopThreadA()));
    connect(threadBButton, SIGNAL(clicked()),
    this, SLOT(startOrStopThreadB()));
    connect(quitButton, SIGNAL(clicked()),
    this, SLOT(close()));

    MyString *p_str =new MyString();

    QObject::connect(
    threadA, SIGNAL(SetMyText (QString, int)),
    p_str, SLOT (set_mes_str(QString, int)) );
    QObject::connect(
    threadB, SIGNAL(SetMyText (QString, int)),
    p_str, SLOT (set_mes_str(QString, int)) );

    }
    void ThreadAB::startOrStopThreadA()
    {
    if (threadA -> isRunning()) {
    threadA -> stop();
    threadAButton -> setText(tr("Start A"));
    } else {
    threadA -> start();
    threadAButton -> setText(tr("Stop A"));
    }
    }
    void ThreadAB::startOrStopThreadB()
    {
    if (threadB -> isRunning()) {
    threadB -> stop();
    threadBButton -> setText(tr("Start B"));
    } else {
    threadB -> start();
    threadBButton -> setText(tr("Stop B"));
    }
    }
    void ThreadAB::closeEvent(QCloseEvent *event)
    {
    threadA -> stop();
    threadB -> stop();
    threadA -> wait();
    threadB -> wait();
    event -> accept();
    }
    @

    MyString.h

    @
    #ifndef MySTRING_H
    #define MySTRING_H
    #include <QMessageBox>
    class MyString : public QObject
    {
    Q_OBJECT

    public:
    

    MyString();

    public slots:
    void set_mes_str(QString, int);
    void show_mes_str();

    signals:
    void mes_str_is_set();

    private:
    QString message_string;
    };
    #endif //MySTRING_H
    @

    MyString.cpp

    @
    #include "MyString.h"
    #include <QDebug>

    MyString::MyString(){
    QObject::connect(
    this, SIGNAL(mes_str_is_set()),
    this, SLOT (show_mes_str() ) );
    }

    void MyString::set_mes_str(QString thread_name, int running_number)
    {
    message_string = thread_name + "->" + running_number;
    qDebug() << "set_mes_str : message_string = " << message_string;
    emit mes_str_is_set();
    }
    void MyString::show_mes_str()/
    {
    QMessageBox msg;
    msg.setText(message_string);
    msg.exec();
    }
    @



  • Let me add: if you put in signal definition {} then compiler finds the function (not signal) ?!


  • Lifetime Qt Champion

    Hi,

    You forgot the Q_OBJECT macro in your MyThread class.

    Don't forget to re-run qmake once you added it.



  • Dear SGaist, thank you very much ! It works now. With best wishes, Dmitri.


  • Lifetime Qt Champion

    You're welcome !

    Since you signals are working now, please update the thread title prepending [solved] so other forum users may know a solution has been found :)


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