How to connect main window menu trigger action to call a method in a sub class?

Hi,

How would you connect an action of main window to have impact on MDI children which are separate classes?

Example:

There are two widgets displayed in an MDI child window, a QTreeView and a QTextEdit.
If user clicks on a checkable menu item, I want the MDI child to show (setVisible false/true) the QTreeView widget according to its state.

Special case: to handle this action separately or for all the windows.

Thank you!