On Wednesday 28 September 2016 21:40:39 Lars wrote:
> On Wed, September 28, 2016 2:24 am, Graeme Geldenhuys wrote:
> > On 2016-09-28 08:38, David Emerson wrote:
> >> I'm testing out CORBA interfaces before changing all my code to use
> >> them (I would prefer not to have managed types for interfaces).
> >
> > I've been using CORBA style interfaces for years,
>
> Curious, where do corba interfaces come in handy ?
Assume there is a support-function or -class, for example TStatFiler from
MSEgui, which stores and reads values to/from streams. It must call the
appropriate read and write functions in the client classes. It is possible to
define the functions in a common ancestor of the clients as "virtual
abstract" which enforces a single client-class hierarchy which often is
impossible to achieve.
The solution are interfaces but not the default COM-interfaces with their
reference counting nightmare but the not reference counted CORBA-interfaces -
which is a wrong name BTW because they have nothing to do with CORBA.
Clients of TStatReader/TStatWriter must implement the interface:
"
istatfile = interface(iobjectlink)[miid_istatfile]
procedure dostatread(const reader: tstatreader);
procedure dostatwrite(const writer: tstatwriter);
procedure statreading;
procedure statread;
function getstatvarname: msestring;
function getstatpriority: integer;
end;
"
iobjectlink provides basic object communication functionality:
"
iobjectlink = interface(inullinterface)
procedure link(const source,dest: iobjectlink; valuepo: pointer = nil;
ainterfacetype: pointer = nil; once: boolean = false);
procedure unlink(const source,dest: iobjectlink; valuepo: pointer = nil);
//source = 1 -> dest destroyed
procedure objevent(const sender: iobjectlink; const event: objecteventty);
function getinstance: tobject;
end;
"
inullinterface is an empty CORBA-style interface:
"
{$interfaces corba}
inullinterface = interface
//no referencecount
end;
"
If a client registers at TStatFiler it provides its "istatfile" pointer which
will be stored in a list in TStatFiler. TStatfiler will use this list in
order to call the necessary functions and procedures of the clients if
reading/writing has been triggered.
MSEgui extensively uses CORBA-interfaces.
Martin
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