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Thread: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its status?

  1. #1
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    Default How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its status?

    I wrote the code attacched & it work (in editobject.cpp find the text "QUESTION:" and read my comment) but i want to know if is it possible with just a connect signal/call (i make my apologise for my bad english) to have the discrimination of what QCheckBox inserted in a QList<QCheckBox*> change its status?
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  2. #2
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    Default Re: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its statu

    Read about QObject::sender().

  3. The following user says thank you to Lesiok for this useful post:

    andreaQt (2nd October 2020)

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    Default Re: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its statu

    please more info

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    Default Re: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its statu

    QObject::sender() gives you the pointer to the QObject (in your case the QCheckBox) instance that emitted the signal that the slot is handling. So if you have multiple check boxes connected to the same slot, you can use sender() to determine which checkbox sent the signal.

    Qt Code:
    1. // Your member variable that stores your checkboxes
    2. QList<QCheckbox *> myListOfCheckboxes;
    3.  
    4. // Slot connected to QCheckBox::toggled() signal
    5. void MyWidget::onCheckboxToggled( bool bChecked )
    6. {
    7. int whichBox = myListOfCheckboxes.indexOf( sender() );
    8. }
    To copy to clipboard, switch view to plain text mode 
    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

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    Default Re: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its statu

    OK but i have no idea about to write (to catch the signal):
    connect (list_check_box, ????, ...., ????);
    or how the slot is called?

    and when i try to implement in my code:
    Qt Code:
    1. void EditObject::onCheckboxToggled(bool bChecked)
    2. {
    3. int whichBox = list_check_box->indexOf(sender());
    4. }
    To copy to clipboard, switch view to plain text mode 
    i have this error -> error: reference to type 'QCheckBox *const' could not bind to an rvalue of type 'QObject *'
    Last edited by andreaQt; 2nd October 2020 at 19:10.

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    Default Re: How emit signal when a QCheckBox inserted in a QList<QCheckBox*> change its statu

    Qt Code:
    1. for ( auto index; index < numberOfCheckBoxes; ++index )
    2. connect( list_check_box[ index ], &QCheckBox::toggled, this, &MyWidget::onCheckboxToggled );
    To copy to clipboard, switch view to plain text mode 

    Of course, you can't call connect() until after you have created all of your checkboxes and put them into the QList.

    Qt Code:
    1. QCheckBox * pCB = qobject_cast< QCheckBox * >( sender() );
    2. int whichBox = list_check_box.indexOf( pCB );
    To copy to clipboard, switch view to plain text mode 

    list_check_box should be defined as "QList< QCheckBox *>" so you use "." to call methods, not "->". There is no reason to define list_check_box as a "QList<QCheckBox *> *".
    <=== The Great Pumpkin says ===>
    Please use CODE tags when posting source code so it is more readable. Click "Go Advanced" and then the "#" icon to insert the tags. Paste your code between them.

  8. The following user says thank you to d_stranz for this useful post:

    andreaQt (2nd October 2020)

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