delphi - Delphi XE2 中的类助手和类拦截器

Question

我有一段代码，如下所示:

界面部分:

TControlOrganizer = class(TComponent)  // a kind of List of TControl
private
  FList : TList;  //Handling list of TControl
  ..............
end;

TControlHelperAdd = class // Just for separating value entered by user and value produced by code
  private
    FOrganizer : TControlOrganizer;
    FOrigValue : String;
    FUserValue : String;
end;

TControlHelper = class helper for TControl  //Basic helper for TControl
  private
    class var
      FAddProp : TControlHelperAdd;
  protected
    procedure SetOrganizer(Value : TControlOrganizer);
    function getOrganizer:TControlOrganizer;
  public
    class Constructor doinit;
    class Destructor deinit;
    procedure OrganizerChanged;virtual;
  published
    Property Organizer:TControlOrganizer read getOrganizer write setOrganizer; //Problem No.1
  end;

//Helper for CustomEdit inherited from TControlHelper
TCustomEditHelper = class helper(TControlHelper) for TCustomEdit
  protected
    procedure OrganizerChanged;override;
  end;
//TEdit : interceptor
TEdit= class(StdCtrls.TEdit)
  protected
    procedure Change;override;  //problem No.3
end;

实现部分:

{TControlHelper}

class Constructor TControlHelper.doinit;
begin
  FAddProp :=TControlHelperAdd.Create;
end;

class Destructor TControlHelper.deinit;
begin
  FreeAndNil(FAddProp);
end;

procedure TControlHelper.OrganizerChanged;
begin
end;

procedure TControlHelper.SetOrganizer(Value : TControlOrganizer);
begin
  if FAddProp.FOrganizer<>value then begin
     if assigned(FAddProp.FOrganizer) then begin
       FAddProp.FOrganizer.remove(self);
     end;
     FAddProp.FOrganizer:=value;
     if assigned(FAddProp.FOrganizer) then begin
       FAddProp.FOrganizer.Add(self);
     end;
     OrganizerChanged;  //Problem No.2
  end;
end;

function TControlHelper.getOrganizer:TControlOrganizer;
begin
  result:=FAddProp.FOrganizer;
end;

{TCustomEditHelper}
procedure TCustomEditHelper.OrganizerChanged; //problem No.2
begin
  if assigned(FAddProp) then begin
    if assigned(Organizer) then begin
      FAddProp.FOrigValue:=Text;
      FAddProp.FUserValue:=Text;
    end;
  end;
end;

{TEdit = Interceptor} 
procedure TEdit.Change; //Problem No.3
begin
  inherited Change;
  FAddProp.FUserValue:=Text;
end;

我发现了 3 个我自己无法解决的问题。

问题 1:已发布的属性不会显示在对象检查器中。我想我犯了一个错误，忘记了一些东西。

问题2:如上所示，类帮助器中的重写方法没有触发(不起作用)。

问题3:如上所示，拦截器类中的重写方法没有触发(不起作用)。

谁能帮我找出问题所在吗？感谢您的帮助，并对我糟糕的英语表示歉意。

Answer 1

问题1

A published property in a helper does not show up in the Object Inspector.

没错。在助手中声明的属性永远不会出现在对象检查器中。

问题2

Virtual methods have no effect in class helpers.

这又是设计使然。尽管编译器允许您在帮助程序中定义虚拟方法，但它没有任何效果。为了触发 TCustomEditHelper.OrganizerChanged，TCustomEditHelper 需要成为目标对象的事件助手。

问题3

The Change method for my intercepted TEdit class does not fire.

那是因为您没有实例化拦截的TEdit。如果实例化正确的类，即您定义的拦截器类，该方法将触发。