Re: How To Check if an object is created (instantiated)?

Locke wrote:

> Delphi newbie speaking here so this could be wrong.
> 
> But I thought you could do something like:
> 
> if not Assigned(R) then
> begin
>   // Do stuff with R
> end;

A beginner's mistake, indeed. A variable is not necessarily set to nil
before it is used. If it is a local variable, it will be placed on the
stack, and the value it has (not that R is a pointer) is simply what
was there before the routine started.

Assigned can only check if something is nil, i.e. it can only check for
one defined value. Anything that is not nil can either be a valid
pointer or junk. No way to tell the difference, unless you use it and
it goes haywire (this is not necessarily the case!). Then you know it
wasn't valid. <g>

More here:

  http://rvelthuis.de/articles/articles-pointers.html#badpointers

-- 
Rudy Velthuis        http://rvelthuis.de

"It is better to have a permanent income than to be fascinating."
 -- Oscar Wilde (1854-1900)