a Free procedure call doesn't free (and nil) an object

Posted on 2003-10-22
Last Modified: 2010-04-05
hi everyone,

i have the following problem :
i've created a TTimer descendent the following way :


  TMyTimer = Class(TTimer)
                    ... various variables and TList Objects...
                    constructor Create(aowner : TComponent);override;
                    destructor destroy; override;

var MyTimer : TMyTimer;

constructor TPopUpCampagne.Create(AOwner : Tcomponent);
     inherited Create(AOwner);
     ... several initializations including OnTimer affectation ...

destructor TPopUpCampagne.destroy;
     ... stuff to free memory...

     inherited destroy;

then, further in the source code, i do the following (i want to destroy MyTimer to re-create it - instead of updating its data) :

if Assigned(Mytimer) then;



the problem is that after the free call, the variable MyTimer isn't Nil - as expected ! but is still pointing to an existing object (and then my program throws an exception on another operation).

i've run the debugger and all the free calls in the object hierarchy are done.

Does anyone have an idea about what's happening ? and does anyone have a workaround ?
i could recreate the variable with the MyTimer:=TMyTimer.Create(Nil); but then i would have a memory leak...

thanks in advance,


PS : i put 150 points, cause it's important and i need a quick answer...
Question by:fsurfer
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
LVL 27

Accepted Solution

kretzschmar earned 150 total points
ID: 9597806
instead of

if Assigned(Mytimer) then;


if Assigned(Mytimer) then

meikl ;-)
LVL 27

Expert Comment

ID: 9597824
just for eplanation

>the problem is that after the free call, the variable MyTimer isn't
>Nil - as expected !

the referenceVariable is never set to nil after calling the free-method,
thats a normal bahaviour, you as developer have to care about this

meikl ;-)
LVL 27

Expert Comment

ID: 9597853
btw. your timer is freed

Author Comment

ID: 9598092
Thanks for the answer !

it works perfectly !

i've always believe that free was doing a FreeAnd Nil....hmmmm there're always things to learn :)

LVL 27

Expert Comment

ID: 9598159
glad to helped you ;-)

Featured Post

On Demand Webinar: Networking for the Cloud Era

Did you know SD-WANs can improve network connectivity? Check out this webinar to learn how an SD-WAN simplified, one-click tool can help you migrate and manage data in the cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
NetCrunch network monitor is a highly extensive platform for network monitoring and alert generation. In this video you'll see a live demo of NetCrunch with most notable features explained in a walk-through manner. You'll also get to know the philos…
This tutorial will teach you the special effect of super speed similar to the fictional character Wally West aka "The Flash" After Shake : All lightning effects with instructions : http://www.mediaf…
Suggested Courses
Course of the Month5 days, 11 hours left to enroll

627 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question