program System_EventArgs;

{$APPTYPE CONSOLE}
{$AUTOBOX ON}


type
  // FireEventArgs: a custom event inherited from EventArgs.
  FireEventArgs = class(EventArgs)
  private
    FFerocity: integer;
    FRoom: string;
  public
    constructor Create(room: string; 
                       ferocity: Integer); 
                       override;
    property Room : string read FRoom;
    property Ferocity : integer read FFerocity;
  end;

  // Event and a Class with a function that creates 
  // the eventargs and initiates the event
  FireEventHandler = procedure(sender: System.Object; 
                               fe: FireEventArgs) of object;
  FireAlarm = class
  private
    FFireEvent : FireEventHandler;
  public
    // event "FireEvent" whose type is 
    // our FireEventHandler "delegate".
    property FireEvent : FireEventHandler add FFireEvent 
                                          remove FFireEvent;
    // This will be the starting point 
    // of our event-- it will create FireEventArgs,
    // and then raise the event, passing FireEventArgs.
    procedure ActivateFireAlarm(room: string;
                                ferocity: Integer);
  end;

  FireHandlerClass = class
  public
    constructor Create(_fireAlarm: FireAlarm); override;
  strict private
    // This is the function to be executed 
    // when a fire event is raised
    procedure ExtinguishFire(sender: System.Object; 
                             fe: FireEventArgs);
  end;

  FireEventTest = class
  public
    class procedure Main;
  end;


{ FireEventArgs }

constructor FireEventArgs.Create(room: string; 
                                 ferocity: Integer);
begin
  inherited Create;
  // The fire event will have 
  // two pieces of information
  // 1) Where the fire is, and
  // 2) How "ferocious" it is.
  self.FRoom := room;
  self.FFerocity := ferocity;
end;

{ FireAlarm }

procedure FireAlarm.ActivateFireAlarm
        (room: string; ferocity: Integer);
var
  fireArgs: FireEventArgs;
begin
  
  // Raise the event by invoking the delegate. 
  // Pass in the object that initated the 
  // event (self) as well as FireEventArgs.
  // The call must match the signature 
  // of FireEventHandler.

  if Assigned(FFireEvent) then
  begin
    fireArgs := FireEventArgs.Create(room, 
                                     ferocity);
    FFireEvent(self, fireArgs);
  end;
end;

{ FireHandlerClass }

constructor FireHandlerClass.Create(_fireAlarm: FireAlarm);
begin
  inherited Create;
  
  // Add a delegate containing the ExtinguishFire 
  // function to the class'
  // event so that when FireAlarm is raised, 
  // it will subsequently execute ExtinguishFire.
  Include(_fireAlarm.FireEvent, ExtinguishFire);
end;

procedure FireHandlerClass.ExtinguishFire
             (sender: TObject; fe: FireEventArgs);
begin
  Console.WriteLine(''#10'The ExtinguishFire function
                     was called by {0}.', sender.ToString);
  if (fe.ferocity < 2) then
    Console.WriteLine('This fire in the {0} 
                       is no problem.  I''m going to pour 
                       some water on it.', fe.room)
  else
    if (fe.ferocity < 5) then
      Console.WriteLine('I''m using FireExtinguisher to 
                        put out the fire in the {0}.', 
                        fe.room)
    else
      Console.WriteLine('The fire in the {0} is out 
                         of control.  I''m calling the 
                         fire department!', fe.room);
end;

{ FireEventTest }

class procedure FireEventTest.Main;
var
  myFireHandler: FireHandlerClass;
  myFireAlarm: FireAlarm;
begin
  // Create an instance of the class 
  // that will be firing an event
  myFireAlarm := FireAlarm.Create;

  
  // Create an instance of the class that will be 
  // handling the event. Note that
  // it receives the class that will fire 
  // the event as a parameter.
  myFireHandler := FireHandlerClass.Create(myFireAlarm);

  //use our class to raise a few events
  //  and watch them get handled
  myFireAlarm.ActivateFireAlarm('Kitchen', 3);
  myFireAlarm.ActivateFireAlarm('Study', 1);
  myFireAlarm.ActivateFireAlarm('Porch', 5);
end;

//test program
begin
  FireEventTest.Main;
end.