GuiSwitcher is a NoOp node to control the gui expression. It creates knobs which can be switched between its render value and GUI value.
The famous $gui expression will return 1 in the graphic user interface mode and 0 in render-side. It’s great to enable heavy node only when rendering on the farm and disable it when you are working.
By using a tcl if statement you can easily switch from one ui value to another render value.
$gui?1:40 # expr?thenDo:elseDo
In this expression example, it will give you 40 during render and 1 in the GUI. The only problem is that you can’t really see anymore what you are doing. The GuiSwitcher give you the ability to switch on/off the GUI to see what you are rendering and set both render value and gui value for any created knobs.