Question

My TMemo descendant has constructor

constructor TMyMemo.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  Lines.Clear;
end;

When I put TMyMemo on the form I get error “Control ” has no parent window.”. Why?

Answer 1

A newly created memo has no content. But content is added as soon as the component acquires a name, which is done automatically by the designer. To prevent this, remove csSetCaption from ControlStyle:

constructor TMyMemo.Create(AOwner: TComponent); 
begin 
  inherited Create(AOwner); 
  ControlStyle := ControlStyle - [csSetCaption];
end;