Delphi的基於接口(IInterface)的多播監聽器模式（觀察者模式 ），iinterface監聽器

Delphi的基於接口(IInterface)的多播監聽器模式（觀察者模式 ），iinterface監聽器

本文來自：http://www.cnblogs.com/hezihang/p/6083555.html

Delphi采用接口方式設計模塊，可以降低模塊之間的耦合，便於擴展和維護。本文提供一個實現基於接口(IInterface)方式的監聽器模式（觀察者模式、訂閱者模式），實現一個自動多播器。

下面程序在Berlin下測試通過，其他Delphi版本未測試，未進行跨平台測試（應該可以支持）

1.prepare

在觀察者模式中采用接口，可以將相關函數匯合為接口。

舉例：假設我們窗口有一個TTreeView，用於顯示應用中的對象，用戶通過點擊TreeView中的不同對象，切換其他多個不同窗口中的顯示內容。

在傳統的方式下，維護一個通知列表，可以采用TreeView.OnChange事件中調用所有通知，然後處理如下：（也可采用多播方式，詳見：http://www.cnblogs.com/hezihang/p/3299481.html）

procedure TForm2.TreeView1Change(Sender: TObject; Node: TTreeNode);
var
  L:TTVChangedEvent;
begin
  for L in FList do  //FList：TList<TTVChangedEvent>
    L(Sender, Node);
end;

顯然采用傳統方式，各窗口都需要uses TreeView所在窗口。

另外，如果TreeView所在窗口還有其他事件需要對多個外部窗口或對象進行通知，

則再需要建立一個通知列表。

采用事件方式，需要自己維護一個或多個通知列表，同時各個使用事件的單元都需要引用事件源的單元。

 2.

如果我們采用接口方式，將所有事件包含進去，由TreeView所在窗口去調用：

type
  {$M+}
  ICurrentStateObserver=interface
     ['{20E8D6CB-3BCF-4DAE-A6CE-FEA727133C57}']
     procedure OnCurrentObjectChange(CurObj:Pointer);
     procedure OnDataReceive(Buf:Pointer; Size:Integre);
     procedure OnResize(W, H:Integer);
  end;
  {$M-}

注意實現自動觀察者的接口必須打開RTTI，{$M+}

然後，只需要如下調用，就可以讓所有監聽者（觀察者）的OnResize被調用(接口內所有方法均可被調用）：

procedure TForm2.FormResize(Sender: TObject);
begin
  CurrentStateDispatcher.Source.OnResize(Width, Height);
end;

其中：

(1).

CurrentStateDispatcher.Source:ICurrentStateObserver

是一個虛擬接口，也是ICurrentStateObserver類型。調用此接口內的方法，就自動調用所有觀察者所對應方法。

這樣我們只需要調用

CurrentStateDispatcher.Source.OnCurrentObjectChange(...);
CurrentStateDispatcher.Source.OnDataReceive(...);
CurrentStateDispatcher.Source.OnResize(...);

就可以實現所有觀察者的調用。

(2).

CurrentStateDispatcher:IInterfaceObservable<ICurrentStateObserver>

IInterfaceObservable<ICurrentStateObserver>是一個實現ICurrentStateObserver的多播監聽器模式（觀察者模式）的接口：

  IInterfaceObservable < T: IInterface >= interface
    procedure AddObserver(const aListener: T);
    procedure RemoveObserver(const aListener: T);
    function GetSource: T;
    property Source: T read GetSource;
  end;

AddObserver是添加監聽者，RemoveObject是刪除觀察者

Source就是前面提到的用於多播調用的虛擬接口。

(3).在使用模式的對象中聲明:

  TForm2=class(TForm)
  ....
  private
     FCurrentStateDispatcher:IInterfaceObservable<ICurrentStateObserver>;
  public
    property CurrentStateDispatcher:IInterfaceObservable<ICurrentStateObserver> read FCurrentStateDispatcher;
  end;

3.

下面我們看一個完整的使用例子：
uMainForm.pas

unit uMainForm;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs , uInterfaceObservable, Vcl.StdCtrls,
  Vcl.ComCtrls;

type
  {$M+}
  ITestObserver=interface
  ['{FE7F7C11-13BC-472A-BB7A-6536E20BCEDD}']
    procedure OnClick(Sender:TObject);
    procedure OnResize(Sender:TObject; X, Y:Integer);
  end;
  {$M-}

  TForm2=class;
  TObserver1=class(TInterfacedObject, ITestObserver)
    F:TForm2;
    procedure OnClick(Sender:TObject);
    procedure OnResize(Sender:TObject; W, H:Integer);
    constructor Create(Owner:TForm2);
  end;

  TObserver2=class(TInterfacedObject, ITestObserver)
    F:TForm2;
    procedure OnClick(Sender:TObject);
    procedure OnResize(Sender:TObject; W, H:Integer);
    constructor Create(Owner:TForm2);
  end;

  TForm2 = class(TForm)
    Memo2: TMemo;
    procedure FormClick(Sender: TObject);
    procedure FormResize(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
private
    { Private declarations }
    FTestDispatcher:IInterfaceObservable<ITestObserver>;
  public
    { Public declarations }
    property TestDispatcher:IInterfaceObservable<ITestObserver> read FTestDispatcher;
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.FormClick(Sender: TObject);
begin
  FTestDispatcher.Source.OnClick(Sender);
end;

procedure TForm2.FormCreate(Sender: TObject);
begin
    FTestDispatcher:=TDioInterfaceDispatcher<ITestObserver>.Create;
    FTestDispatcher.AddObserver(TObserver1.Create(Self));
    FTestDispatcher.AddObserver(TObserver2.Create(Self));
end;

procedure TForm2.FormDestroy(Sender: TObject);
begin
   FTestDispatcher:=nil;
end;

procedure TForm2.FormResize(Sender: TObject);
var
//  i:Integer;
//  T:LongWord;
  W, H:Integer;
begin
  W:=Width;
  H:=Height;
//  T:=GetTickCount;
//  for i := 0 to 1000000 do
  TestDispatcher.Source.OnResize(Sender, W, H);
//  ShowMessage(IntToStr(GetTickCount- T));
end;

{ TObserver1 }

constructor TObserver1.Create(Owner: TForm2);
begin
  F:=Owner;
end;

procedure TObserver1.OnClick(Sender: TObject);
begin
  F.Memo2.Lines.Add('TObserver1.OnClick');
end;

procedure TObserver1.OnResize(Sender: TObject; W, H:Integer);
begin
  F.Memo2.Lines.Add(Format('TObserver1.OnResize:%d, %d', [W, H]));
end;

{ TObserver2 }

constructor TObserver2.Create(Owner: TForm2);
begin
  F:=Owner;
end;

procedure TObserver2.OnClick(Sender: TObject);
begin
  F.Memo2.Lines.Add('TObserver2.OnClick');
end;

procedure TObserver2.OnResize(Sender: TObject; W, H:Integer);
begin
  F.Memo2.Lines.Add(Format('TObserver2.OnResize:%d, %d', [W, H]));
end;

end.

uMainForm.dfm

object Form2: TForm2
  Left = 0
  Top = 0
  Caption = 'Form2'
  ClientHeight = 309
  ClientWidth = 643
  OnClick = FormClick
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  OnResize = FormResize
  TextHeight = 13
  object Memo2: TMemo
    Left = 0
    Top = 152
    Width = 643
    Height = 157
    Align = alBottom
    TabOrder = 0
  end
end

 4.

 下面是uInterfaceObservable.pas

unit uInterfaceObservable;

interface

uses System.Generics.Collections, System.TypInfo, System.Rtti;

type
  IInterfaceObservable < T: IInterface >= interface
    procedure AddObserver(const aListener: T);
    procedure RemoveObserver(const aListener: T);
    function GetSource: T;
    property Source: T read GetSource;
  end;

  TDioInterfaceDispatcher<T: IInterface> = class(TInterfacedObject, IInterfaceObservable<T>)
  protected
    class var FTypeInfo: PTypeInfo;
    class var FMethods: TArray<TRttiMethod>;
    class var FIID: TGUID;
    class constructor Create;
  protected
    FList: TList<T>;
    FVirtualSource, FSource: T;
    FVirtualInterface: TVirtualInterface;
    FEvents: TObjectList<TList<TMethod>>;
    procedure MethodInvoke(Method: TRttiMethod; const Args: TArray<TValue>;
      out Result: TValue);
  public
    procedure AddObserver(const aListener: T);
    procedure RemoveObserver(const aListener: T);
    function GetSource: T;
    constructor Create;
    destructor Destroy; override;
    property Source: T read FSource;
  end;

implementation

uses System.SysUtils;

{ TDioDispatcher<T> }

procedure TDioInterfaceDispatcher<T>.AddObserver(const aListener: T);
type
  TVtable = array [0 .. 3] of Pointer;
  PVtable = ^TVtable;
  PPVtable = ^PVtable;
var
  i: Integer;
  M: TMethod;
  P: Pointer;
begin
  FList.Add(aListener);
  P:=IInterface(aListener);
//  P := IInterfaceGetObject(aListener).GetObject;
  for i := 0 to FEvents.Count - 1 do
  begin
    // 3 is offset of Invoke, after QI, AddRef, Release
    M.Code := PPVtable(P)^^[3 + i ] ;
    M.Data := P;
    FEvents[i].Add(M);
  end;
  if FList.Count=1 then
    FSource:=aListener
  else
    FSource:=FVirtualSource;
end;

procedure TDioInterfaceDispatcher<T>.MethodInvoke(Method: TRttiMethod;
  const Args: TArray<TValue>; out Result: TValue);
var
  L:TList<TMethod>;
  M:TMethod;
  i:Integer;
begin
  L:=FEvents[Method.VirtualIndex-3];
  i:=0;
  while i<L.Count do
  begin
    M:=L[i];
    Args[0]:=M.Data;
    System.Rtti.Invoke(M.Code, Args, Method.CallingConvention, nil);
    if (M=L[i]) then
      Inc(i);
  end;
end;

constructor TDioInterfaceDispatcher<T>.Create;
var
  i: Integer;
  LMethod: TRttiMethod;
  E: TList<TMethod>;
  S:String;
begin
  inherited Create;
  FEvents := TObjectList<TList<TMethod>>.Create(True);
  FList := TList<T>.Create;
  FVirtualInterface := TVirtualInterface.Create(FTypeInfo);
  FVirtualInterface.OnInvoke := Self.MethodInvoke;
  FVirtualInterface.QueryInterface(FIID, FVirtualSource);
  Assert(Assigned(FVirtualSource), '未找到接口' + GUIDToString(FIID));
  FSource:=FVirtualSource;
  for i := 0 to High(FMethods) do
  begin
    E := TList<TMethod>.Create;//TEvent.Create(LMethod, FTypeInfo, i);
    FEvents.Add(E);
  end;
end;

class constructor TDioInterfaceDispatcher<T>.Create;
var
  LType: TRttiType;
  FContext: TRttiContext;
begin
  FTypeInfo := TypeInfo(T);
  LType := FContext.GetType(FTypeInfo);
  FIID := TRttiInterfaceType(LType).GUID;
  FMethods := LType.GetMethods();
  //Assert(Length(FMethods) <= 30, '只能分發30個以內函數的接口！');
end;

destructor TDioInterfaceDispatcher<T>.Destroy;
var
  i: Integer;
begin
  FSource := nil;
  FVirtualSource:=nil;
  FVirtualInterface := nil;
  FList.DisposeOf;
  FEvents.DisposeOf;
  inherited;
end;

function TDioInterfaceDispatcher<T>.GetSource: T;
begin
  Result := FSource;
end;

procedure TDioInterfaceDispatcher<T>.RemoveObserver(const aListener: T);
var
  N, i: Integer;
begin
  N := FList.IndexOf(aListener);
  if N >= 0 then
  begin
    for i := 0 to FEvents.Count - 1 do
      FEvents[i].Delete(N);
  end;
  FList.Remove(aListener)
end;

end.