Question

I would like to add to my component the conditional state when the component cannot be loaded and inform its user (developer) that this component cannot be loaded in design time and target user at runtime (safely somehow, if possible).

How can I prevent the component from loading in its constructor and how to display message (exception) from constructor safely at design time and at runtime ?

constructor TSomeComponent.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);

  if csDesigning in ComponentState then
    if SomeIncompatibleCondition then
      begin
        // how to display message (exception) about the wrong 
        // condition and interrupt the loading of the component ?
      end;

  // is it possible to do the same at runtime ?
end;

Thank you

Answer 1

Raise an exception, eg:

constructor TSomeComponent.Create(AOwner: TComponent); 
begin 
  inherited Create(AOwner); 
  if SomeIncompatibleCondition then 
    raise Exception.Create('Incompatible condition detected!');
end;