delphipt.pas

Delphi高级开发指南是开发程序的好帮手

unit DelphiPt;

interface

uses
  Classes, Graphics;

type
  TDDHPoint = class (TCollectionItem)
  private
    fX, fY: Integer;
  public
    Text: string;
    procedure WriteText (Writer: TWriter);
    procedure ReadText (Reader: TReader);
    procedure DefineProperties (Filer: TFiler); override;
    procedure Paint (Canvas: TCanvas);
    procedure Assign (Pt: TPersistent); override;
  published
    property X: Integer read fX write fX;
    property Y: Integer read fY write fY;
  end;

  TWrapper = class (TComponent)
  private
    FColl: TCollection;
  published
    property MyColl: TCollection read FColl write FColl;
  public
    constructor Create (Owner: TComponent); override;
    destructor Destroy; override;
  end;

implementation

// TWrapper constructor and destructor

constructor TWrapper.Create (Owner: TComponent);
begin
  inherited Create (Owner);
  FColl := TCollection.Create (TDDHPoint);
end;

destructor TWrapper.Destroy;
begin
  FColl.Clear;
  FColl.Free;
  inherited Destroy;
end;


// class TDDHPoint methods

procedure TDDHPoint.WriteText (Writer: TWriter);
begin
  Writer.WriteString (Text);
end;

procedure TDDHPoint.ReadText (Reader: TReader);
begin
  Text := Reader.ReadString;
end;

procedure TDDHPoint.DefineProperties (Filer: TFiler);
begin
  Filer.DefineProperty (
    'Text', ReadText, WriteText, (Text <> ''));
end;

procedure TDDHPoint.Paint (Canvas: TCanvas);
begin
  Canvas.Ellipse (fX - 3, fY - 3, fX + 3, fY + 3);
  Canvas.TextOut (fX + 5, fY + 5, Text);
end;

procedure TDDHPoint.Assign (Pt: TPersistent);
begin
  if Pt is TDDHPoint then
  begin
    fx := TDDHPoint (Pt).fX;
    fY := TDDHPoint (Pt).fY;
    Text := TDDHPoint (Pt).Text;
  end
  else
    // raise an exception
    inherited Assign (pt);
end;

//initialization
//RegisterClass (TWrapper);
end.