uses
  ..., TypInfo;

function TForm1.IsAPropExist(AInst: TObject; const PropName: string): Boolean;
var
  PropInfo: PPropInfo;
begin
  Result := False;
  PropInfo := GetPropInfo(AInst, PropName);
  if PropInfo <> nil then
    Result := PropInfo.Name = PropName;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to Self.ComponentCount - 1 do
  begin
    if IsAPropExist(Self.Components[i], 'Caption') then
      SetPropValue(Self.Components[i], 'Caption', IntToStr(i));
  end;
end;

-------------------------------------------------------------------------------

uses
  ..., TypInfo;

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
  aComponent: TComponent;
  PropInfo: PPropInfo;
  ViewText, ViewHint: string;
begin
  ViewText := 'Hello world'; // for debug use, you should comment these 2 lines
  ViewHint := 'the hint';    //   and then implement GetInfoByName method.

  for i := 0 to ComponentCount - 1 do
  begin
    aComponent := Components[i];
    PropInfo := GetPropInfo(aComponent.ClassInfo, 'Caption');
    if not Assigned(PropInfo) then // Caption property of aComponent NOT exists
    begin
      // turn to search Text property
      PropInfo := GetPropInfo(aComponent.ClassInfo, 'Text');
      if not Assigned(PropInfo) then // Text property of aComponent NOT exists
        Continue;
    end;

    // comes here, either Caption or Text property must exists
    // first, find the ViewText and ViewHint of the aComponent by the name
    // GetInfoByName(aComponent.Name, ViewText, ViewHint);
    SetStrProp(aComponent, PropInfo, ViewText);

    // then, search Hint property
    PropInfo := GetPropInfo(aComponent.ClassInfo, 'Hint');
    if Assigned(PropInfo) then
      SetStrProp(aComponent, PropInfo, ViewHint);
  end;
end;