Every module has at least one editor interface. Some modules have several editors, such as a source (.pas) file and form description (.dfm) file. All editors implement the IOTAEditor interface; cast the editor to a specific type to learn what kind of editor it is. For example, to obtain the form editor interface for a unit, you can do the following:

{ Return the form editor for a module, or nil if the unit has no form. }
function GetFormEditor(Module: IOTAModule): IOTAFormEditor;
var
  I: Integer;
  Editor: IOTAEditor;
begin
  for I := 0 to Module.ModuleFileCount - 1 do
  begin
    Editor := Module.ModuleFileEditors[I];
    if Supports(Editor, IOTAFormEditor, Result) then
      Exit;
  end;
  Result := nil;
end;

// Return the form editor for a module, or 0 if the unit has no form.
_di_IOTAFormEditor __fastcall GetFormEditor(_di_IOTAModule module)
{
for (int i = 0; i < module->ModuleFileCount; ++i)
{
_di_IOTAEditor editor = module->ModuleFileEditors[i];
_di_IOTAFormEditor formEditor;
if (editor->Supports(formEditor))
return formEditor;
}
return 0;
}

The editor interfaces give you access to the editor's internal state. You can examine the source code or components that the user is editing, make changes to the source code, components, or properties, change the selection in the source and form editors, and carry out almost any editor action that the end user can perform. 

Using a form editor interface, a wizard can access all the components on the form. Each component (including the root form or data module) has an associated IOTAComponent interface. A wizard can examine or change most of the component's properties. If you need complete control over the component, you can cast the IOTAComponent interface to INTAComponent. The native component interface enables your wizard to access the TComponent pointer directly. This is important if you need to read or modify a class-type property, such as TFont, which is possible only through NTA-style interfaces.