Regarding 4
doesn't the application free _all_ its assigned memory when it is
closed? Or would some component that was constructed with a nil owner
keep using that memory until some other event - if so, when would that
be - reboot/shutdown/next Delphi app started ? I'm aware this is not a
nice way of doing things, but just wondered the official reason.
Cheers,
Kurt.
Neven MacEwan wrote:
>
> Chrissy
>
> Just a few basics
>
> 1/ In Delphi you almost never have to use pointers and new() is really for
> non-object use
> 2/ A TComponent derived class can own other TComponents (which may own
> other...) See TComponent.Components array & TComponent.ComponentCount
> (simarly TWinControl implement Controls array and ControlCount)
> 3/ By default a 'Form' (a TComponent Derivative) owns all the components on
> it
> 4/ The 'owner' is passed to the constuctor if the 'owner' is nil then
> something has to destroy it
> This is because the TComponent constructor 'registers' itself with the owner
> (who maintains a list of it components)
> so that it knows who to destroy (in its destructor).
> 5/ It is imperitive to understand the difference between Parent and Owner
> 6/ It is imperitive to understand the difference between
> TObject/TPersistent/TComponent
>
> I think in various versions of Delphi the overhead of components traversing
> lists and registering a list of components (and the
> sequencing of destuction) was annoying so it became fashionable to
> programmatically create components with a nil Owner
> and Destroy them yourself however in my experience it is better to go throuh
> the pain of passing an owner and working though
> the consequences (esp with visible components because there is invariably a
> link between ownership and parenthood) than
> continue the 'trick'
>
> Simple Aint it
> HTH
>
> Regards Neven
> N.K. MacEwan B.E. E&E
> Ph 649 574 0027
> Fax 649 570 2706
>
> "A truth denied the light of action will wither to a promise, propaganda and
> then a lie"
>
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