Why I'm getting error on undefinded reference on object slot

[thippu]

hi,
I have a plot class object in mainwindow class
In mainwindow class, I did connect plot class object and whenever mainwindow object's button is clicked,
Syntax is fine,I think
But why I'm getting error?

here plot header file:

class Plot: public QwtPlot
{
    Q_OBJECT

   public:
    Plot( QWidget * = NULL );
    virtual ~Plot();

    void start();
    virtual void replot();

    virtual bool eventFilter( QObject *, QEvent * );

public Q_SLOTS:
    void setIntervalLength( double );
    void setCh1();

And
mainwindow cpp:

MainWindow::MainWindow( QWidget *parent ):
    QWidget( parent )
{
    const double intervalLength = 1.0; // refered in seconds,used to sets the x scale and also Display widget to intervalLength

    d_plot = new Plot( this );
    d_plot->setIntervalLength( intervalLength );//sets the x scale by intervalLength

    d_amplitudeKnob = new Knob( "Amplitude", 0.0, 200.0, this );
    d_amplitudeKnob->setValue( 50.0 );

    d_frequencyKnob = new Knob( "Frequency [Hz]", 0.1, 20.0, this );
    d_frequencyKnob->setValue( 2.5 );

    d_intervalWheel = new WheelBox( "Displayed [s]", 1.0, 100.0, 1.0, this );//display wheel
    d_intervalWheel->setValue( intervalLength );

    d_timerWheel = new WheelBox( "Sample Interval [ms]", 0.0, 20.0, 0.1, this );//sample wheel
    d_timerWheel->setValue( 10.0 );


    ch1=new QPushButton("Turn on ch1",this);
    ch2=new QPushButton("Turn on ch2",this);
    ch3=new QPushButton("Turn on ch3",this);
    ch4=new QPushButton("Turn on ch4",this);

    QVBoxLayout *hchannelLayout=new QVBoxLayout();
    hchannelLayout->addWidget(ch1);
    hchannelLayout->addWidget(ch2);
    hchannelLayout->addWidget(ch3);
    hchannelLayout->addWidget(ch4);

    QVBoxLayout* vLayout1 = new QVBoxLayout();
    vLayout1->addWidget( d_intervalWheel );
    vLayout1->addWidget( d_timerWheel );
    vLayout1->addStretch( 5 );
    vLayout1->addLayout(hchannelLayout);
    vLayout1->addWidget( d_amplitudeKnob );
    vLayout1->addWidget( d_frequencyKnob );


    QHBoxLayout *layout = new QHBoxLayout( this );
    layout->addWidget( d_plot, 10 );
    layout->addLayout( vLayout1 );


    connect( d_amplitudeKnob, SIGNAL( valueChanged( double ) ),
        SIGNAL( amplitudeChanged( double ) ) );
    connect( d_frequencyKnob, SIGNAL( valueChanged( double ) ),
        SIGNAL( frequencyChanged( double ) ) );
    connect( d_timerWheel, SIGNAL( valueChanged( double ) ),
        SIGNAL( signalIntervalChanged( double ) ) );

    connect( d_intervalWheel, SIGNAL( valueChanged( double ) ),
        d_plot, SLOT( setIntervalLength( double ) ) );


    connect(ch1,SIGNAL(clicked()),
            d_plot,SLOT(setCh1()));
}

error:
build-oscilloscope-Desktop_Qt_5_9_0_MinGW_32bit-Debug/moc/moc_plot.cpp:75: undefined reference to `Plot::setCh1()'
collect2.exe: error: ld returned 1 exit status

So, What to do?

[mrjj]

Hi
Completely delete build folder.
and see.
seems ok.

[J.Hilk]

@thippu
also make sure, your setCh1 function has a body in your plot.cpp file.

[thippu]

@J.Hilk @mrjj Thank you,those were the mistake
Now it is building the project.
:) thank you guys

[mrjj]

super
So was it a missing body ?

[thippu]

@mrjj Yes