How to save a document?

Hallo,
I’m developing an app in AS studio and have to handle table view datas.
To save and open datas the procedures ‘on data representation’ and ‘on load data representation’ are working well. The saved files have only an empty sheet as an
icon; is there a possibility to show that icon with my own added icon?
Before closing the window I want to ask the user for saving or not. The ‘should close’ handler doesn’t work (not even a beep). The ‘will close’ handler has reactions, but it is not possible to prevent closing for ‘cancel’. How is that problem to solve?
Before quitting the app, I want also to ask the user for saving or not. I tried it with a ‘should quit’ handler, but without success. I show you my attempt below.

Sorry for my bad English and thank you for your help.
Heiner

on should quit theObject
	if hasChanged then
		set theWindow to front window
		
		set theReply to display dialog "Änderungen vor dem Schließen sichern?" 
buttons {"Nicht sichern", "Abbrechen", "Sichern"} default button "Sichern" with icon 0 -- attached to window theWindow (it does not work)
		set theAnswer to button returned of theReply
		
		if theAnswer is "Nicht sichern" then -- not saving
			return true
		else if theAnswer is "Abbrechen" then -- cancel
			return false
		else if theAnswer is "Sichern" then -- save
			
			tell save panel
				set title to "Noten Oberstufe: Sichern"
				set prompt to "Sichern"
				-- set treat packages as directories to false
			end tell
			
			set theResult to display save panel with file name "OhneNamen"
			if theResult is 1 then -- Save
			
				--  the 4 following lines are the same as in the 'on data representation'-handler:
				set schuelerdaten to data source of table view "daten" of scroll view "daten" of theWindow
				set dieDaten to contents of every data cell of every data row of schuelerdaten
				set theSortColumn to sort column of schuelerdaten
				
				set theData to {daten:dieDaten, sortColumnName:name of theSortColumn, sortColumnOrder:sort order of theSortColumn}
				
				-- I don't know, if these is necessary:
				set longFileName to path name of save panel
				set fileName to POSIX path of longFileName
				
				-- nothing to say about that:
				save theData in file fileName
				return true
			else if theResult is 0 then -- Cancel
				return false
			end if
		end if
	else
		return true
	end if
end should quit

Model: eMac
Browser: Safari 312
Operating System: Mac OS X (10.3.9)

Problems are solved!

Hi there! Was wondering your solution for the docs you are saving and their icons. Under the Target Editor in xCode under Properties - > Documents Types, I’ve set my own extension and Icon file, but after building and saving a file the icon isn’t allocated to the doc. I know my icon file is OK.

Any idea?

Danke.

Michael