Re: Interface and struct
From: Bill McCarthy
Date: 04/01/04
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Date: Thu, 1 Apr 2004 13:54:41 +1000
Hi Bob,
nested classes and structures are only useful for hiding and access to the outer
classes private scoped members. So, you are probably best NOT to nest the
struct.
eg:
Class Foo: Implements IFace
...
End Class
Structure Bar
..
End Sturcture
Interface IFace
..
End Interface
That is, keep them all separate. I have a feeling you are use to structs being
like UDT's in Vb6, which they are in many ways, but they are also more like a
class in many ways too. Most importantly, they do not have to be declared
inside a class, but can be declared just like any class can be.
Bill
"Bob Clegg" <bclegg@clear.net.nz> wrote in message
news:u3IZmE2FEHA.3880@TK2MSFTNGP09.phx.gbl...
> Hi Bill,
> The class is right.
> The interface declaration is more like
> Function UpdateBar(myBar as Bar) as boolean
>
> The problem is that it seems to me that Bar should no longer live in Foo,
> now that Foo is hiding behind an interface. ( The reason for this is that
> Foo is a data class using SQL Server objects and there is soon going to be
> an FooBrother that uses Oracle data objects. Only one of the two will be
> compiled depending on the installation.) So where to place Bar?
> As a number of calling classes want to use Bar it would seem ideal to me to
> place it in a module.
> But if I do that then the above declaration fails with can't expose a
> friend type.
> I have a working solution by getting Bar to bunk down in one of the calling
> classes, but it seems tacky.
> regards
> Bob
>
> "Bill McCarthy <no spam>" <bill_mcc @ iprimus.com.au> wrote in message
> news:uNBBaCyFEHA.3576@tk2msftngp13.phx.gbl...
> > Hi Bob,
> >
> > Do you mean you have :
> >
> > Class Foo
> > Public Structure Bar
> > ...
> > End Structure
> > End Class
> >
> > and you want to define an Interface, such as :
> >
> > Public IFace
> > Function GetBar() as Foo.Bar
> > End Interface
> >
> > If so, Foo must be Public.
> > Alternatively, don't have Bar nested.
> >
> >
> >
> > Bill.
> >
> >
> >
> > "Bob Clegg" <bclegg@clear.net.nz> wrote in message
> > news:OoEhpzvFEHA.712@tk2msftngp13.phx.gbl...
> > > Hi,
> > > I have a Data Class that declares a Public struct.
> > > It accepts instances of this struct in some of its function calls.
> > > I now want to put an interface between this class and the calling
> classes.
> > >
> > > I would like to move the struct out to the module that is housing the
> > > interface.
> > >
> > > But when I do this I get a scoping problem.
> > >
> > > The interface declaration of any function that is passing one of these
> > > structs complains that it can't expose a friend type publicly.
> > >
> > > I have tried putting the struct into the interface and I have also tried
> a
> > > public declaration in the module proper and another module.
> > >
> > > The only thing that seems to work but doesn't sit comfortably with me is
> to
> > > declare it public in one of the calling classes.
> > > Any thoughts?
> > > thanks
> > > Bob
> > >
> > >
> > >
> >
> >
>
>
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