Delphi 实现 事件分发机制

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  PMethod = ^TMethod;

  TMutliEvent = procedure(const Value ,value2: string) of object;

  TMultiEventClass = class
  private
    fMultiEventHandlers : TList;
  public
    constructor Create;
    destructor Destroy; override;

    procedure AddMultiEvent(const Value: TMutliEvent);
    procedure RemoveMultiEvent(const Value: TMutliEvent);

    procedure FireMultiEvent;
  end;

  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    procedure Handler1(const value,value2 : string);
    procedure Handler2(const value,value2 : string);
    procedure Handler3(const value,value2 : string);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TMultiEventClass }

constructor TMultiEventClass.Create;
begin
  inherited Create;
  fMultiEventHandlers := TList.Create;
end;

destructor TMultiEventClass.Destroy;
var
  cnt: Integer;
begin
  for cnt := 0 to -1 + fMultiEventHandlers.Count do
    Dispose(fMultiEventHandlers[cnt]);
  fMultiEventHandlers.Free;

  inherited;
end;

procedure TMultiEventClass.RemoveMultiEvent(const Value: TMutliEvent);
var
  cnt: Integer;
begin
  for cnt := 0 to -1 + fMultiEventHandlers.Count  do
  begin
    if (TMethod(Value).Code = TMethod(fMultiEventHandlers[cnt]^).Code) and
       (TMethod(Value).Data = TMethod(fMultiEventHandlers[cnt]^).Data) then
    begin
      Dispose(fMultiEventHandlers[cnt]);
      fMultiEventHandlers.Delete(cnt);
      Break;
    end;
  end;
end;

procedure TMultiEventClass.AddMultiEvent(const Value: TMutliEvent);
var
  h: PMethod;
begin
  h := New(PMethod);
  h^.Code := TMethod(Value).Code;
  h^.Data := TMethod(Value).Data;
  fMultiEventHandlers.Add(h);
end;

procedure TMultiEventClass.FireMultiEvent;
var
  cnt: Integer;
  msg : string;
begin
  for cnt := 0 to -1 + fMultiEventHandlers.Count do
  begin
    msg := Format('%d/%d %s',[1 + cnt, fMultiEventHandlers.Count, 'fired!']);

    TMutliEvent(fMultiEventHandlers[cnt]^)(msg,'TEST');
  end;
end;

{ TForm1 }
procedure TForm1.Button1Click(Sender: TObject);
var
  test : TMultiEventClass;
begin
  test := TMultiEventClass.Create;
  try
    test.AddMultiEvent(Handler1);
    test.AddMultiEvent(Handler2);
   // test.RemoveMultiEvent(Handler1);
    test.AddMultiEvent(Handler3);

    test.FireMultiEvent;
  finally
    test.Free;
  end;
end;

procedure TForm1.Handler1(const value,value2: string);
begin
  ShowMessage(value2 +'h1:' + value);
end;

procedure TForm1.Handler2(const value,value2: string);
begin
  ShowMessage(value2 + 'h2:' + value);
end;

procedure TForm1.Handler3(const value,value2: string);
begin
  ShowMessage(value2 + 'h3:' + value);
end;

end.