Steve gave a good example but I want to add something. Delphi's RTTI is only
generated for objects descending from TPersistent or objects in {$M+}
sections. TObject has no RTTI attached to it. I find this very important
because RTTI requires lots of space and should only be generated for objects
that actually require it.
This is also of some importance for people moving from other languages to
Delphi: I want them to understand Delphi will not generate RTTI for every
class they write. Delphi only does that upon request!Steve Williams wrote: >>> I understand that TList is a list of pointers. What I cannot >>> understand is >>> why I can't do something like\ >>> >>> for i := 0 to AList.Count do >>> begin >>> if AList.Items[i]^ is TMyObject then >>> with AList.Items[i]^ as TMyObject do >>> >>> etc etc etc. >> >> You can. You just need to tell the compiler that it is a TObject >> first. >> This then allows the compiler to know that you are dealing with an >> object. >> not just a pointer to a block of memory. It needs to know it's an >> object >> so it knows that there is RTTI attached to this block of memory. >> >> for i := 0 to AList.Count - 1 do >> begin >> if TObject(AList.Items[i]) is TMyObject then >> with TMyObject(AList.Items[i]) do >> >> Or even simpler, if you are only adding the same type of object to >> the >> list, then you do not have to check the type. Just typecast. >> >> for i := 0 to AList.Count - 1 do >> begin >> with TMyObject(AList.Items[i]) do >> >>> In other words, I suppose my question is "If TList is a list of >>> TPointer, >>> the how do I dereference the pointer to access the object? Is >>> accessing >>> the >>> Items property the only way to do it?" >> >> You do not dereference the pointer because variables that reference >> objects are really pointers anyway. >> >> Sly >> >> >> >> >> >> This message and its attachments may contain legally privileged or >> confidential information. This message is intended for the use of >> the individual or entity to which it is addressed. If you are not >> the addressee indicated in this message, or the employee or >> agent responsible for delivering the message to the intended >> recipient, you may not copy or deliver this message or its >> attachments >> to anyone. Rather, you should permanently delete this message and >> its attachments and kindly notify the sender by reply e-mail. Any >> content of this message and its attachments, which does not relate >> to the official business of the sending company must be taken not >> to have been sent or endorsed by the sending company or any of its >> related entities. No warranty is made that the e-mail or >> attachment(s) are free from computer virus or other defect. >> > > > >> _______________________________________________ >> Delphi mailing list -> [email protected] >> http://www.elists.org/mailman/listinfo/delphi _______________________________________________ Delphi mailing list -> [email protected] http://www.elists.org/mailman/listinfo/delphi
