In Delphi documentation is specified to not call
Destroy directly. You need to use Free who call
Destroy and verify that Object is not Nil.
Adrian
--- Carl Jacobs <[EMAIL PROTECTED]> a écrit :
---------------------------------
Well who would have believed that FreeAndNil has a bug
in it!
The following code shows the essence of the problem.
type
TA = Class
destructor Destroy;
end;
TB = Class
destructor Destroy;
procedure SomeMethod;
end;
var
A : TA;
B : TB;
destructor TB.Destroy;
begin
FreeAndNil(A);
inherited;
end;
procedure TB.SomeMethod;
begin
{ Some code that references other fields/methods in
TB - The exception occurs at this point };
end;
destructor TA.Destroy;
begin
B.SomeMethod; { If using FreeAndNil, then B is
already nil at this point. SomeMethod is still called,
but with a self of 0 }
inherited;
end;
begin
A : TA.Create;
B : TB.Create;
FreeAndNil(B); <- This fails in TB.SomeMethod.
Because B is set to nil before it's freed.
B.Free; <- This works.
B := nil;
end;
If you check the VCL source code (in Delphi 7 at
least) then it really does Nil before it Frees.
[Non-text portions of this message have been removed]
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Cordialement,
Adrian BUNYI
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