TControl.Parent Property

Indicates the parent of the control.

Pascal

property Parent: TWinControl;

C++

__property TWinControl * Parent;

Description

Use the Parent property to get or set the parent of this control. The parent of a control is the control that contains the control. For example, if an application includes three radio buttons in a group box, the group box is the parent of the three radio buttons, and the radio buttons are the child controls of the group box.

To serve as a parent, a control must be an instance of a descendant of TWinControl.

When creating a new control at runtime, assign a Parent property value for the new control. Usually, this is a form, panel, group box, or some control that is designed to contain another. Changing the parent of a control moves the control onscreen so that it is displayed within the new parent. When the parent control moves, the child moves with the parent.

Some controls (such as ActiveX controls) are contained in native windows rather than in a parent VCL control. For these controls, the value of Parent is nil (Delphi) or NULL (C++) and the ParentWindow property specifies the window.

Note: The Parent property declared in TControl is similar to the Owner property declared in TComponent, in that the Parent of a control frees the control just as the Owner of a component frees that Component. However, the Parent of a control is always a windowed control that visually contains the control, and is responsible for writing the control to a stream when the form is saved. The Owner of a component is the component that was passed as a parameter in the constructor and, if assigned, initiates the process of saving all objects (including the control and its parent) when the form is saved.

C++ Examples:

Copy Code

/*
This example uses a button placed next to a group box. When the
user clicks the button, the group box becomes the parent of the
button, so the button moves inside the group box.
*/
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  if (Button1->Parent != GroupBox1) // second click?
  {
    RemoveControl(Button1);
    GroupBox1->InsertControl(Button1);
  }
}

/*
Note that it was necessary to remove the button from the Controls
property of the form before the button actually moves into the
group box. This code accomplishes the same thing:
*/

void __fastcall TForm1::Button2Click(TObject *Sender)
{
  Button2->Parent = GroupBox1;
}

Delphi Examples:

Copy Code

{
This example uses a button placed next to a group box. When the
user clicks the button, the group box becomes the parent of the
button, so the button moves inside the group box.
} 
procedure TForm1.Button1Click(Sender: TObject);
begin
  if (Button1.Parent <> GroupBox1) then // second click?
  begin
    RemoveControl(Button1);
    GroupBox1.InsertControl(Button1);
  end;
end;

{
Note that it was necessary to remove the button from the Controls
property of the form before the button actually moves into the
group box. This code accomplishes the same thing:
}

procedure TForm1.Button2Click(Sender: TObject);
begin
  Button2.Parent := GroupBox1;
end;