I'm writing some code that programmatically modifies the contents of the notebook it's running in. My code uses NotebookLocate to select all the cells in the notebook that have a particular tag — in my case, they happen to be several non-adjacent Input cells (but not necessarily all input cells in the notebook). Now, I want to clear the contents of those cells, but not delete the cells themselves.

This seems to me like something that ought to be fairly easy, but I'm having a dickens of a time figuring out a way. I know I can get a list of CellObject expressions for the selected cells by calling SelectedCells, but is there some way to write a function I could map onto that list, which takes a CellObject and erases its contents? Or… Ideas?


Updated to address BoxData issue

An alternative to using NotebookDelete is to use NotebookWrite/NotebookRead. Here is a function that clears the contents of a cell:

eraseCellContents[cell_] := NotebookWrite[
    Replace[NotebookRead[cell], Cell[h_, r___] :> Cell[emptyCell[h], r]]

emptyCell[_BoxData] := BoxData[""]
emptyCell[_] := ""

The helper function emptyCell makes sure that cells which use 2D typesetting (e.g., StandardForm) retain their 2D typesetting capabilities.

Example usage:

eraseCellContents /@ SelectedCells[]
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  • $\begingroup$ Wow. I wouldn't have thought of doing something so cryptic -- I guess I'm not yet fluent enough with patterns, delayed rules, and the like. $\endgroup$ – ibeatty Aug 23 '17 at 19:45

Assuming they are all "Input" cells you can do:

   (SelectionMove[#, All, CellContents]; NotebookDelete[]) &
 , SelectedCells[(*notebook*)]

instead of NotebookDelete you can use FrontEndTokenExecute["Clear"]

The assumption about input cell is important because otherwise DefaultDuplicateCellStyle will replace the modified cell's style. (1)

So in general you may want to use this:

    ( SelectionMove[#, All, CellContents]
    ; Internal`WithLocalSettings[
          CurrentValue[#, DefaultDuplicateCellStyle
          ] = Lookup[Developer`CellInformation[#], "Style", "Input"] (*(2)*)
        , NotebookDelete[]
        , CurrentValue[#, DefaultDuplicateCellStyle] = Inherited
     ) &
   , SelectedCells[]

One could argue that it may erase explicit DefaultDuplicateCellStyle set for Cell, but this option is usually set at notebook's level.

(2) How can I get the style of selected cells?

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  • $\begingroup$ Might also be worth mentioning the issue if Editable->False is set $\endgroup$ – b3m2a1 Aug 23 '17 at 19:18
  • $\begingroup$ @b3m2a1 worth a comment for sure, not sure if more attention is required ;) should be obvious. $\endgroup$ – Kuba Aug 23 '17 at 19:32
  • $\begingroup$ Aah. I had been afraid of NotebookDelete because I thought it would always delete the entire cell. $\endgroup$ – ibeatty Aug 23 '17 at 19:39
  • $\begingroup$ @ibeatty I see, don't forget CellContents then :) $\endgroup$ – Kuba Aug 23 '17 at 19:40

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