CODEWITHSUNDEEP
componentsdelphi-xe5
Paul
Paul

Reputation: 26650

Properties of published nested components are not saved, events are not visible in object inspector

I created a component with following contents:

TEditLine = class(TCustomControl)
strict private
  FCaptionLabel: TLabel;
  FUnitLabel: TLabel;
  FEdit: TMyEdit;
end;

Then I started to propagate necessary properties of nested components by creating of corresponding getter/setter pairs.

Suddenly I thought, it may be easier to publish these nested components themselves as read-only properties so that when some new property or method gets introduced to one of these components, no changes in container component interface are required:

TEditLine = class(TCustomControl)
strict private
  FCaptionLabel: TLabel;
  FUnitLabel: TLabel;
  FEdit: TMyEdit;
published
  property CaptionLabel: TLabel read FCaptionLabel;
  property UnitLabel: TLabel read FUnitLabel;
  property Edit: TMyEdit read FEdit;
end;

When I put the component on a form, I see CaptionLabel, UnitLabel and Edit in Object Inspector, but that is all I can achieve.

Is it generally a good idea to do so? How I solve the two issues listed above?

Upvotes: 0

Views: 299

Answers (1)

Remy Lebeau
Remy Lebeau

Reputation: 595837

TComponent-based properties are treated as references to external components by default, unless you call SetSubComponent(True) on the objects that back them, eg:

TEditLine = class(TCustomControl)
strict private
  FCaptionLabel: TLabel;
  FUnitLabel: TLabel;
  FEdit: TMyEdit;
public
  constructor Create(AOwner: TComponent); override;
published
  property CaptionLabel: TLabel read FCaptionLabel;
  property UnitLabel: TLabel read FUnitLabel;
  property Edit: TMyEdit read FEdit;
end;

... 

constructor TEditLine.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  ...
  FCaptionLabel := TLabel.Create(Self);
  FCaptionLabel.Parent := Self;
  FCaptionLabel.SetSubComponent(True); // <-- ADD THIS
  ...
  FUnitLabel := TLabel.Create(Self);
  FUnitLabel.Parent := Self;
  FUnitLabel.SetSubComponent(True); // <-- ADD THIS
  ...
  FEdit := TMyEdit.Create(Self);
  FEdit.Parent := Self;
  FEdit.SetSubComponent(True); // <-- ADD THIS
  ...
end;

Upvotes: 1

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