[inline] On Wed, 29 May 2002 21:51:14 +0100, Ian Griffiths <[EMAIL PROTECTED]> wrote:
>Arild Fines <[EMAIL PROTECTED]> wrote: > >> >FWIW - I think Petzold misunderstood/misrepresented something >> > there. His example was referring to someControl.Size.Width * 2; >> > something which will fail because the Size property will return a >> > copy of the Size struct. >> > >> > Making changes to the Width property of the returned struct will >> > have no effect onthe original and the whole statement is pointless. >> > The compiler recognizes this and issues a warning(or an error - >> > dont remember offhand). > >From: "Jon Jagger" <[EMAIL PROTECTED]> > >> But the whole statement might _not_ be pointless. One of the >> main points of a property is that a write context you don't get >> an assignment you get a set accessor. > >Ah, but this isn't a write context. It was in my original question. >At least it's not for the Size >property. This causes a *get* of the Size. It might then perform a set on >the size struct's Width, but it'll be a copy of the Size that it performs >the set on. And unless the Size were to hold a reference back to its >containing object (which would pretty much defeat the purpose of making it a >value type in the first place) then there's nothing useful that the >Size.Width set accessor can do anyway. That's a bold statement. I myself don't claim to be omnipotent ;-) I can just about image a scenario where it might be useful. Consider a _class_ that contains a property which is not trivial. Suppose the property contains two sub properties that have a mutual constraint (something similar cropped in a posting recently). In this case you might want to provide a top level property _and_ a nested property. In this case making the top level property return a struct containing a reference back to the object might be a useful optimization. Bt be that as it may, my question is still is there a _fundamental_ reason that only compiler writers currently know about (as implied by Petzold). Cheers JJ > >-- >Ian Griffiths >DevelopMentor > >You can read messages from the DOTNET archive, unsubscribe from DOTNET, or >subscribe to other DevelopMentor lists at http://discuss.develop.com. You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
