Constructor and Destructor Example

SystemTime Class: In this final example, we want to create a class that will allow us to store the current time and then to restore it when we are finished with it.

Source Code for our class

unit SystemTime;  

interface

uses

   Windows, Messages, SysUtils, Classes, Graphics,

   Controls, Forms, Dialogs, StdCtrls;  

type

   TSysTime = class(TObject)

   private

     FStartDateTime : TDateTime;

   protected

   { Protected declarations }

   public

     constructor Create; virtual;

     destructor Destroy; override;

      procedure SetOldTime;

   published

   { Published declarations }

end;

implementation

constructor TSysTime.Create; 

begin

   FStartDateTime := Now;

end;

destructor TSysTime.Destroy;

var

   NewTime : TSystemTime;

begin

   DateTimeToSystemTime(FStartDateTime, NewTime);

   SetSystemTime(NewTime); 

end;  

procedure TSysTime.SetOldTime; 

var

   NewTime : TSystemTime;  

begin

   // set time to an arbitrary date/time

   NewTime.wYear := 1996;

   NewTime.wMonth := 1; 

   NewTime.wDayOfWeek    := 1;

   NewTime.wDay := 8;

   NewTime.wHour := 5;

   NewTime.wMinute  := 32;

   NewTime.wSecond  := 22;

   NewTime.wMilliseconds := 10;

   SetSystemTime(NewTime);

 end;

end.