delphi的procedure of object

The delphi Procedure of  Object (a special type of pointer) 
    Theory:      // adapted to implement a particular procedure or function is not a 
          type  
               TNotifyEvent = Procedure (Sender: TObject) of  Object ; 
      First: Procedure is the type of process can be understood as the type, parameters structure definition process, and the specific implementation may be dynamically assigned 
 onclick example above: 
     statement: onclick = procedure (Sender: TObject, a: Integer) of  Object ; after that you can put TNotifyEvent as a process used, irrespective of its realization what features you want in onclik user what is written, is the same 
         IF ASSIGN (onclick) the then  
          onclick; 
     so long as TNotifyEvent can be executed, the program went to execute it, the control is achieved events
     procedure pointer four bytes, stored in the address process. procedure  of  Object 8 bytes, and the address of the address classes save process 
      procedure  of  Object is a class procedure (function class), used as follows: 
          1 , and normal function the same point: can be as general functions and procedures as in the instance of a class called as an object method; 
          2 , different from the ordinary functions: may not through the object, but by a direct call to the class. 
    That is, the general functions and procedures must be invoked through instance (object) type, the process type (function class) may not necessarily be invoked by the instance of the class. Class by calling function or process, can be defined and implemented methods can not or is not suitable as a particular behavior of the object. 
  Application: 
     Delphi often seen in the following two definitions 
     the Type 
         TMouseProc = Procedure (X-, the Y: Integer);   // a conventional process 
         TMouseEvent = Procedure (X-, the Y: Integer) of Object; //A type of object methods 

      both look about the same but the actual meaning is not the same, the difference lies in TMouseEvent type of approach must be a object. A hidden parameter based method has self, both the parameter that is not the same, it is not interchangeable. 
   TMouseProc only a single function pointer type; 
   TMouseEvent is a function pointer to the object, i.e. the object function / class / method of 

 Procedure    TForm1. the BBB (the I: Integer); 
 the begin  
    ShowMessage ( ' the BBB: '    +    the IntToStr (the I)); 
 End ; 

Procedure    TForm1.CCC (the I: Integer); 
 the begin  
    ShowMessage ( ' the CCC: '    +    the IntToStr (the I)); 
 End ; 

Procedure    TForm1.Button1Click (Sender: TObject); 
     of the type  
        TAAA   =    Procedure    (I: Integer)    of    Object    ; 
 var  
    ap: TAAA; 
the begin  
    ap: = BBB; // There is an implicit Self, full format: self.BBB; where the method of assigning the BBB variable ap, attention BBB ap prototype and declared to be the same, otherwise there will be wrong 
    ap ( 1 ); 
    ap: =    CCC; 
    ap ( 2 ); 
 End ; 




Unit Unit1; 

interface 

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

type 
  TForm1 = class(TForm) 
    edt1: TAdvEdit; 
    edt2: TAdvEdit; 
    btn1: TButton; 
    procedure btn1Click (Sender: TObject);
  private 
    { Private declarations } 
  public 
     procedure myonExit (sender: TObject);
  over ; 

was 
  Form1: TForm1; 

implementation 

{ $ R * .dfm } 
procedure TForm1.myonExit (sender: TObject);
begin 
  if tadvedit (transmitter) .text = ' a '  then 
  begin 
    Show Message ( ' a ' );
  Over 
  presence 
  IFtadvedit (transmitter) .text = ' B '  then 
  begin 
    Show Message ( ' b ' );
  over ;
over ; 

procedure myonExit2 (sender: TObject);
 begin 
   if tadvedit (transmitter) .text = ' c '  then 
    begin 
      Show Message ( ' C ' );
    Over 
    presence 
    IF tadvedit (transmitter) .text = ' d '  then 
    begin 
      Show Message ( ' d ' );
    over ;
 End ; 

Procedure TForm1.btn1Click (Sender: TObject);
 type 
  X1 = Procedure (SENDER: TObject) of  Object ; 
  X2 = Procedure (SENDER: TObject);
 var 
  Y1: X1; 
  Y2: X2; 
the begin 
  Y1: = myonExit; // with hidden Self 
  = myonExit2;: Y2 // without hidden Self 

  Y1 (edt1); // edt box is a pop-up message box a or b or b 
  ; Y2 (edt1) // when c or d is a block edt pop-up message box c or d 

  // edt1.OnExit: = myonExit; // use Not myonExit2 CAN 
End ; 



End .