I have to write a program for physical application. I want to write in the following way.

ui file

QLinedit // Inputting data of the System
QPushButton // Caculate und Quit
QwtPlot // Output of an simple Plot

if you push the Button calculate -> the curve will be plotted into the qwtplot widget.
if you push Quit the programm has to close
In the lineedits you can put data for the function or curve with is show in the qwtplot widget after putting calculate.

I don't get the communication between the different objects

How works the communication between line Edit and qwtplot?
How works the communication between ui and qwtplot
How works the communication between QPushButton an qwtplot

In the qwt examples are no ui connection show, help me how communicate with the object of the ui?