delphi - 使用 'anonymous' 类实现 Delphi 接口(interface)

Question

我有一个界面。

type IProgressObserver = interface(IInterface)
    procedure ReportProgress(Progress:Integer);
    procedure ReportError(Message:string);
end;

我已经使用命名类实现了该接口(interface)，如下所示:

type TProgressObserver=class(TInterfacedObject, IProgressObserver)    
    procedure ReportProgress(Progress:Integer);
    procedure ReportError(Message:string);
end;

... implementation of methods go here .....

addProgressObserver(TProgressObserver.Create);

是否可以在不声明类的情况下创建此接口(interface)的实例？像这样的(想象的)代码，它会做与上面相同的事情:

 addProgressObserver(IProgressObserver.Create()
 begin
   procedure ReportProgress(Progress:Integer)
   begin
     ShowMessage('Progress Observed!');
   end

   procedure ReportError(Message:string)
   begin
     Log(Message);
   end
 end;);

Delphi有匿名过程，但是它有匿名类吗？

我找到了this similar question ，但它是用 Java 编写的。

我使用的是Delphi 2010

Answer 1

您可以获得相当匿名的效果，使用匿名方法实现接口(interface)。但是您没有获得对此的实际编译器支持，您必须自己声明所有匿名方法类型，然后实现实际的“匿名”类。给定您的 IProgressObserver 接口(interface)，实现将如下所示:

type
  // This is the interface we'll be dealing with.
  IProgressObserver = interface(IInterface)
    procedure ReportProgress(Progress:Integer);
    procedure ReportError(Message:string);
  end;

  // This will help us anonymously create implementations of the IProgressObserver
  // interface.
  TAnonymousObserverImp = class(TInterfacedObject, IProgressObserver)
  type
    // Declare reference types for all the methods the interface needs.
    TReportProgressProc = reference to procedure(Progress:Integer);
    TReportErrorProc = reference to procedure(Message:string);
  strict private
    FReportProgressProc: TReportProgressProc;
    FReportErrorProc: TReportErrorProc;

    // Actual implementation of interface methods.
    procedure ReportProgress(Progress:Integer);
    procedure ReportError(Message:string);
    // private constructor, so we'll forced to use the public "Construct" function
    constructor Create(aReportProgressProc: TReportProgressProc; aReportErrorProc: TReportErrorProc);
  public
    // This takes the required anonymous methods as parameters and constructs an anonymous implementation
    // of the IProgressObserver interface.
    class function Construct(aReportProgressProc: TReportProgressProc; aReportErrorProc: TReportErrorProc): IProgressObserver;
  end;

{ TAnonymousObserverImp }

class function TAnonymousObserverImp.Construct(
  aReportProgressProc: TReportProgressProc;
  aReportErrorProc: TReportErrorProc): IProgressObserver;
begin
  // Call the private constructor
  Result := TAnonymousObserverImp.Create(aReportProgressProc, aReportErrorProc);
end;

constructor TAnonymousObserverImp.Create(
  aReportProgressProc: TReportProgressProc; aReportErrorProc: TReportErrorProc);
begin
  inherited Create;
  // We simply save the references for later use
  FReportProgressProc := aReportProgressProc;
  FReportErrorProc := aReportErrorProc;
end;

procedure TAnonymousObserverImp.ReportError(Message: string);
begin
  // Delegate to anonymous method
  FReportErrorProc(Message);
end;

procedure TAnonymousObserverImp.ReportProgress(Progress: Integer);
begin
  // Delegate to anonymous method
  FReportProgressProc(Progress);
end;

一旦所有代码就位，您就可以编写如下代码:

var i: IProgressObserver;
begin
  i := TAnonymousObserverImp.Construct(
    procedure (Progress:Integer)
    begin
      // Do something with Progress
    end
    ,
    procedure (Message:string)
    begin
      // Do something with Message
    end
  )
end;

对我来说看起来很匿名!鉴于 Delphi 中匿名方法的实现，它也相当快速且有效。