Creating UNDO Functionality in Oracle Forms

 Retrieving data from the database and changing the data is really easy. But what, if the user changes data and want to do an UNDO?

Doing a new query is the easiest way. The limitations are:

- in a multi-record-block you have to position in the correct record after the query
- if the query was executed via ENTER-QUERY mode you can't jump to the old record because the query-result has changed.

So you have to use a new technique.

The solution is this function. All database-items get their old values back:

PROCEDURE Undo IS
  V_Block  VARCHAR2 (30) := :SYSTEM.CURSOR_BLOCK;
  V_Field  VARCHAR2 (61);
  V_Item   VARCHAR2 (61);
BEGIN
  Validate (Item_Scope);
  IF :SYSTEM.RECORD_STATUS = 'CHANGED' THEN
    V_Field := Get_Block_Property (V_Block, FIRST_ITEM);
    V_Item := V_Block || '.' || V_Field;
    WHILE V_Field IS NOT NULL
    LOOP
      IF Get_Item_Property (V_Item, ITEM_TYPE) 
         IN ('DISPLAY ITEM', 'CHECKBOX', 'LIST', 
             'RADIO GROUP',  'TEXT ITEM')
      AND Get_Item_Property (V_Item, BASE_TABLE) = 'TRUE' 
      THEN
        COPY (Get_Item_Property (V_Item, DATABASE_VALUE), 
              V_Item);
      END IF;
      V_Field := Get_Item_Property (V_Item, NextItem);
      V_Item := V_Block || '.' || V_Field;
    END LOOP;
  END IF;
END;

Best practice is to start this undo-procedure from a menu (e.g. EDIT - UNDO) or handle it through a shortcut.

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