delphi - 如何覆盖继承的属性？

Question

我有一个类(TMyClass)，它有一个属性(Items:TItems)

TItems = class;    

TMyClass = class(TComponent)
private
   FItems: TItems;
   procedure SetItems(const Value: TItems);
protected

public

protected
  property Items: TItems read FItems write SetItems;
end.

TExItems = class(TItems)
private
  FNewProb: Integer;
protected

public

published
  property NewProp: Integer read FNewProb write FNewProb;
end.

TExMyClass = class(TMyClass)
private
   FItems: TExItems;
   procedure SetItems(const Value: TItems);
protected

public

published
  property Items: TExItems read FItems write SetItems;
end.

新的“Items”属性是从TItems继承的，但是当我安装组件时，TExItems的新属性“NewProb”没有出现，看起来“Items”属性仍然是TItems而不是TExItems...如何覆盖它？

谢谢

修改:这是真正的代码

类型 TKHAdvSmoothDock = 类；

TKHAdvSmoothDockItem = class(TAdvSmoothDockItem)
private
  FImageIndex: TImageIndex;
  procedure SetImageIndex(const Value: TImageIndex);
protected

public

published
  property ImageIndex: TImageIndex read FImageIndex write SetImageIndex default -1;
end;

TKHAdvSmoothDockItems = class(TAdvSmoothDockItems)
private
  FOwner: TKHAdvSmoothDock;
  FOnChange: TNotifyEvent;
  function GetItem(Index: Integer): TKHAdvSmoothDockItem;
  procedure SetItem(Index: Integer; const Value: TKHAdvSmoothDockItem);
protected
  function GetOwner: TPersistent; override;
public
  constructor Create(AOwner: TKHAdvSmoothDock);
  function Add: TKHAdvSmoothDockItem;
  function Insert(Index: Integer): TKHAdvSmoothDockItem;
  property Items[Index: Integer]: TKHAdvSmoothDockItem read GetItem write SetItem; default;
  procedure Delete(Index: Integer);
published
  property OnChange: TNotifyEvent read FOnChange write FOnChange;
end;

TKHAdvSmoothDock = class(TAdvSmoothDock)
private
  FImageChangeLink: TChangeLink;
  FImages: TCustomImageList;
  FItems: TKHAdvSmoothDockItems;
  procedure ImageListChange(Sender: TObject);
  procedure SetImages(const Value: TCustomImageList);
  procedure SetItems(const Value: TKHAdvSmoothDockItems);
  function GetItems: TKHAdvSmoothDockItems;
  { Private declarations }
protected
  procedure UpdateImagesFromImageList;
public
  constructor Create(AOwner: TComponent); override;
  destructor Destroy; override;
published
  property Images: TCustomImageList read FImages write SetImages;
  property Items: TKHAdvSmoothDockItems read GetItems write SetItems;
end;

问候。

Answer 1

属性 getter 和 setter 可以是虚拟的，然后通过继承类覆盖，请参阅下面的更新示例。您的示例代码有一个警告，那就是您正在尝试更改属性的类型，这是不允许的。我建议您检查 TExMyClass.SetItems 中的 Value is TExItems 但使用继承的 Items 属性并在 TExMyClass 的所有方法中强制转换为 TExItems 和更多继承人。

TItems = class;

TMyClass = class(TComponent)
private
   FItems: TItems;
   procedure SetItems(const Value: TItems); virtual;
protected
  property Items: TItems read FItems write SetItems;
end;

TExItems = class(TItems)
private
  FNewProb: Integer;
protected

public

published
  property NewProp: Integer read FNewProb write FNewProb;
end;

TExMyClass = class(TMyClass)
private
   procedure SetItems(const Value: TItems); override;
end;