how to connect an openfile signal to a widget slot?

[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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