TCollection & TCollectionitem Tutorial

[TiGü]

Probiere das folgende Konsolenprogramm mal aus, vielleicht hilft dir das weiter:

Delphi-Quellcode:

program Project3;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils, System.Classes;

type
  TMyCollectionItem = class(TCollectionItem)
  private
    // hier kannst du auch eigene Felder und Methoden definieren
  protected
    function GetDisplayName: string; override;
  end;

  TMyCollection = class(TCollection)
  protected
    procedure Update(Item: TCollectionItem); override;
    procedure SetItemName(Item: TCollectionItem); override;
    procedure Notify(Item: TCollectionItem; Action: TCollectionNotification); override;
  public
    procedure BeginUpdate; override;
    procedure EndUpdate; override;
  end;

procedure TMyCollection.BeginUpdate;
begin
  inherited;
  Writeln('BeginUpdate');
end;

procedure TMyCollection.EndUpdate;
begin
  inherited;
  Writeln('EndUpdate');
end;

procedure TMyCollection.Notify(Item: TCollectionItem; Action: TCollectionNotification);
begin
  inherited;
  case Action of
    cnAdded: Writeln(Item.DisplayName + ' added');
    cnExtracting:
      Writeln(Item.DisplayName + ' extracing');
    cnDeleting:
      Writeln(Item.DisplayName + ' deleting');
  end;
end;

procedure TMyCollection.SetItemName(Item: TCollectionItem);
begin
  inherited;
   Writeln(Item.DisplayName + ' ItemName');
end;

procedure TMyCollection.Update(Item: TCollectionItem);
begin
  inherited;
  if Assigned(Item) then
  begin
    // Ein einzelnes Item wurde befummelt
    Writeln(Item.DisplayName + ' updated');
  end else
    // wenn Item = nil, dann ist die ganze Collection betroffen

end;

function TMyCollectionItem.GetDisplayName: string;
begin
  Result := 'HuiBui: ' + IntToStr(Self.ID);
end;

procedure Main;
var
  MyCollection: TMyCollection;
  MyItem: TCollectionItem;
  I: Integer;
  Something: string;
begin
  MyCollection := TMyCollection.Create(TMyCollectionItem);
  try
    MyCollection.BeginUpdate;
    try
      for I := 0 to 10 - 1 do
      begin
        MyItem := MyCollection.Add;
      end;
    finally
      MyCollection.EndUpdate;
    end;

    Something := '';
    for I := 0 to MyCollection.Count - 1 do
    begin
      MyItem := MyCollection.Items[I];
      Something := Something + MyItem.DisplayName + ' ';
    end;

    Writeln(Something);

    MyCollection.Items[5].DisplayName := 'asdf';

    MyCollection.Delete(5);
  finally
    MyCollection.Free;
  end;
end;

begin
  try
    Main;
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

end.