Emit signal to different widget

[unix7777]

I have being searching in the net for solution of this problem and every body write advices but obviously for all like me that ask is hard to understand it without see the code.Because of that i write an example and only need to be written the part i and many others in the net don't understand.

There is a main widget with a Label and button.When click the button a new Dialog opens which contains lineEdit field and a close button.
How we can get the text from dialog's lineEdit field and when close the dialog to set it to the main widget label.
Please see the attached simple project.