Example 5: Synthetic placeholders in delete prompts

Uses OnGetVariableValue to resolve a <var>VarID</var> placeholder that does not correspond to any field of the active dataset.

Scenario

The delete confirmation should name the order, the customer, and who is currently logged in - the first two are dataset fields, the third is not:

FGrid.DelRowQuestion := 'Delete order <var>OrderNo</var> for <var>CustomerName</var>'
  + ', confirmed by <var>CurrentUser</var>?';

The handler

procedure TfrmOrders.GridGetVariableValue(VarID: string; var Value: string);
begin
  if SameText(VarID, 'CurrentUser') then
    Value := Session.LoggedInUserName
  else
    Value := '?';  // unrecognized placeholder - keep it visible instead of blank
end;

Why it works this way

• Only called for a genuine miss: OrderNo and CustomerName above resolve directly from the current row’s fields and never reach this handler at all - it only fires for CurrentUser, which Table.FindField('CurrentUser') would not find.
• One handler, several unrelated placeholders: DelRowQuestion, DelRowsQuestion, and DelRowCaption all resolve through the same handler - VarID is the only way to tell which placeholder is being asked for, there is no separate parameter identifying which string property triggered it.
• Silent fallback if unassigned: leaving OnGetVariableValue unassigned replaces an unresolved <var> with an empty string rather than raising - the else branch above ('?') is a deliberate choice to make a typo in a placeholder name visible in the prompt instead of silently vanishing.

See Also

• OnGetVariableValue
• DelRowQuestion
• TEgDBGridGetVariableValue
• Examples