how to connect an openfile signal to a widget slot?

[fatecasino]

Hi,

thanks to the great documentation/tutorials/fora,
I managed to set up the menubar with QAction. Now I face this problem

error: ‘my2dPlot* MyWidget::mainPlot’ is private

error: ‘my2dPlot* MyWidget::mainPlot’ is private

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when i try to add this line to the openfile action

widget->mainPlot->plotMainCurve(fileName);

widget->mainPlot->plotMainCurve(fileName);

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-widget is the central widget of the mainWindow
-mainPlot is a class that I have created to plot 2d plots
-plotMainCurve is the method to plot the selected data file


This is seems to be a typical hierarchy error. But how can i overcome it and call the function to plot the curve of a specific data file (filename= "data.txt")?

[fatecasino]

before it was:

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
private:
    my2dPlot *mainPlot;
....
{

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
private:
    my2dPlot *mainPlot;
....
{

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and now i moved the mainPlot member to the public:

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    my2dPlot *mainPlot;
....
{

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
    my2dPlot *mainPlot;
....
{

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I don't know if it is a real solution and/or safe thing to do. But how else could i call the plotMainCurve(filename) of the my2dPlot class form the mainwindow?

[FelixB]

I don't know if it is a real solution and/or safe thing to do. But how else could i call the plotMainCurve(filename) of the my2dPlot class form the mainwindow?

you could write a getter method:

my2dPlot* Get2DPlot() {return my2dplot;} const;

my2dPlot* Get2DPlot() {return my2dplot;} const;

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[fatecasino]

yeah, but I don't want to receive the plot. The plot belongs to the my2dPlot class. I just want to send the datafile that I want to print. As you see the hierarchy goes:

widget->mainPlot->plotMainCurve(fileName);

widget->mainPlot->plotMainCurve(fileName);

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[stampede]

What about

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
public slots:
    void plotFromFile( const QString& file ){
        this->mainPlot->plotMainCurve(file);
    }
private:
    my2dPlot *mainPlot;
....
{

class MyWidget : public QWidget
{
public:
    MyWidget(QWidget *parent = 0);
public slots:
    void plotFromFile( const QString& file ){
        this->mainPlot->plotMainCurve(file);
    }
private:
    my2dPlot *mainPlot;
....
{

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?

[fatecasino]

@stampede: it worked like a charm!!
thank you very much..I always really confused with the usage of "this"
What is the actual difference between the two lines??

this->mainPlot->plotMainCurve(file);

this->mainPlot->plotMainCurve(file);

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widget->mainPlot->plotMainCurve(fileName);

widget->mainPlot->plotMainCurve(fileName);

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[FelixB]

"this" is a pointer to the object which "posesses" the current method.

the difference is that the second line "widget->mainPlot..." works only if "mainPlot" is public. That's why I recommended to create a getter. The following would have worked too:

widget->Get2DPlot()->plotMainCurve(file)

widget->Get2DPlot()->plotMainCurve(file)

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[stampede]

What is the actual difference between the two lines??

You use "this" keyword from class methods when you refer to actualy used class instance ( the object that "calls" the method or access the class member ).
Of course you have access to all members of the class in this case.

Here

widget->mainPlot->plotMainCurve(fileName);

you use some object "widget" to call the method. You can access only public members of the "widget" object ( unless you are a friend of a class )

This basic knowledge is mandatory in C++ programming, I really recommend some reading before going into qt programming ( you can find some useful info here: http://www.qtcentre.org/threads/29-W...ourite-C-books )