Delphi 界面助手/解决方法

Question

我意识到Delphi不支持接口助手，但是在阅读了几个SO主题和Spring4D等资源之后，我想知道有没有什么方法可以实现以下？源代码 cmets 几乎总结了我正在尝试做的事情，所以这里是：

program IHelper;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  Spring,
  System.SysUtils;

type

  IMyThing = interface
  ['{01E799A5-9141-4C5E-AA85-B7C9792024D9}']
    procedure BasicThing;
  end;

  TMyThing = class(TInterfacedObject, IMyThing)
  strict private
    procedure BasicThing;
  end;

  IMyThingHelper = record
  private
    FOutage: IMyThing;
  public
    class operator Implicit(const Value: IMyThing): IMyThingHelper;
    procedure HelpfulThing;
  end;

  TMyThingHelper = class helper for TMyThing
  public
    class procedure ObjectThing;
  end;

{ TOutage }

procedure TMyThing.BasicThing;
begin
  Writeln('Basic Thing');
end;


{ IOutageHelper }

procedure IMyThingHelper.HelpfulThing;
begin
  Writeln('Helpful thing');
end;

class operator IMyThingHelper.Implicit(const Value: IMyThing): IMyThingHelper;
begin
  Result.FOutage := Value;
end;

{ TMyThingHelper }

class procedure TMyThingHelper.ObjectThing;
begin
  Writeln('Object thing');
end;

var
  LThing: IMyThing;

begin
  try
    LThing := TMyThing.Create;
    LThing.BasicThing;
    //LThing.HelpfulThing;               // <--- **** prefer this syntax but obviously does not compile
    IMyThingHelper(LThing).HelpfulThing; // <--- this works ok but prefer not to have to cast it here

    //LThing.ObjectThing;                // <--- obviously does not compile
    (LThing as TMyThing).ObjectThing;    // <--- class helpers work ok but no good for interfaces

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

关于如何使此代码在 **** 显示的地方工作的任何想法或建议？ 我知道答案可能是彻底的“不”，但似乎有一些非常聪明的解决方法正在完成，也许比我聪明得多的人知道怎么做？ (德尔福 XE5)

另一个例子

var
   dataObject: IDataObject;

//Get clipboard IDataObject
OleGetClipboard({out}dataObject);

//Check if they want us to move or copy what's on the clipboard
preferredDropEffect: DWORD := dataObject.GetPreferredDropEffect;

//...do the stuff with the clipboard

//Tell them what we did
dataObject.SetPerformedDropEffect(DROPEFFECT_NONE); //we moved the underlying data; sender need not do anything
dataObject.SetPasteSucceeded(DROPEFFECT_MOVE); //Paste complete

有一个助手：

TDataObjectHelper = interface helper for IDataObject
public
   function GetPreferredDropEffect(DefaultPreferredDropEffect: DWORD=DROPEFFECT_NONE): DWORD;
end;

function TDataObjectHelper.GetPreferredDropEffect(DefaultPreferredDropEffect: DWORD=DROPEFFECT_NONE): DWORD;
begin
{
    DROPEFFECT_NONE   = 0;  //Drop target cannot accept the data.
    DROPEFFECT_COPY   = 1;  //Drop results in a copy. The original data is untouched by the drag source.
    DROPEFFECT_MOVE   = 2;  //Drag source should remove the data.
    DROPEFFECT_LINK   = 4;  //Drag source should create a link to the original data.
    DROPEFFECT_SCROLL = 0x80000000 //Scrolling is about to start or is currently occurring in the target. This value is used in addition to the other values.
}
    if TDataObjectHelper.ContainsFormat(Source, CF_PreferredDropEffect) then
        Result := TDataObjectHelper.GetUInt32(Source, CF_PREFERREDDROPEFFECT)
    else
        Result := DefaultDropEffect;
end;

Answer 1

有两种方法可以实现：

• 有一个变量IMyThingHelper 并将您的接口分配给它，然后在记录变量上调用“扩展方法”。

• 另一个是使用absolute:

---

var
  LThing: IMyThing;
  LHelper: IMyThingHelper absolute LThing;
begin
  LThing := TMyThing.Create;
  LHelper.HelpfulThing;

---

不久前我在博客上写过这个issue。不幸的是，在我的情况下，“帮助记录”Enumerable<T> 有太多通用方法，以至于编译器的速度大大降低。

Answer 2

为什么不直接使用另一个界面？

program IHelper;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  Spring,
  System.SysUtils;

type

  IMyThing = interface
  ['{01E799A5-9141-4C5E-AA85-B7C9792024D9}']
    procedure BasicThing;
  end;

  IMyThingHelper = interface
  ['{...}']
    procedure HelpfulThing;
  end;

  TMyThing = class(TInterfacedObject, IMyThing, IMyThingHelper)
  strict private
    procedure BasicThing;
    procedure HelpfulThing;
  end;

{ TOutage }

procedure TMyThing.BasicThing;
begin
  Writeln('Basic Thing');
end;

{ IOutageHelper }

procedure TMyThing.HelpfulThing;
begin
  Writeln('Helpful thing');
end;

var
  LThing: IMyThing;
  LHelper: IMyThingHelper;
begin
  try
    LThing := TMyThing.Create;
    LThing.BasicThing;
    if Supports(LThing, IMyThingHelper, LHelper) then
      LHelper.HelpfulThing;
    Readln;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.