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Thread: How to emit signal from static method?

  1. #1
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    Default How to emit signal from static method?

    Hi I have tried to emit signal from static method in this way .


    Qt Code:
    1. MainWidget* pThis;
    2. MainWidget *MainWidget:: _instance = 0;
    3.  
    4. MainWidget::MainWidget(QWidget *parent):QWidget(parent)
    5. {
    6. pThis = this;
    7. }
    8. MainWidget* MainWidget::getInstance()
    9. {
    10. if(!_instance)
    11. _instance = new MainWidget();
    12. return _instance;
    13. }
    14. void MainWidget :: emitMySignal(){
    15. qDebug()<<"emitMySignal";
    16. pThis->emit mySignal ();
    17. }
    18. MainWidget::~MainWidget()
    19. {
    20.  
    21. }
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    and the call to static function and signal slot connection is here

    Qt Code:
    1. MainWidget::getInstance()->emitMySignal();
    2. qDebug()<<"after emitCall back....";
    3. QObject::connect(MainWidget::getInstance(),SIGNAL(mySignal()),this,SLOT(connectToSlot()));
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    But this is not happening for me .
    Plz suggest

  2. #2
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    Default Re: How to emit signal from static method?

    you connected the slot after emitted the signal.

    try with

    Qt Code:
    1. QObject::connect(MainWidget::getInstance(),SIGNAL(mySignal()),this,SLOT(connectToSlot()));
    2. MainWidget::getInstance()->emitMySignal();
    3. qDebug()<<"after emitCall back....";
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    what is the static method??
    Last edited by mcosta; 20th July 2011 at 08:48. Reason: updated contents
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    Default Re: How to emit signal from static method?

    Qt Code:
    1. pThis = this; //pThis is global, don't do this, you never know what it contains unless, ctor as private
    2.  
    3. void MainWidget :: emitMySignal(){ //I assume this is non static function, if not make it non-static function
    4. qDebug()<<"emitMySignal";
    5. //pThis->emit mySignal ();
    6. emit mySignal(); //this will work
    7. }
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    Default Re: How to emit signal from static method?

    You can't emit signal from static methods, because static methods are not part of an objects instance, they are global, in the scope of the class, which means, you don't have a "sender" object for them.
    You could send an event though.
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