You can't use the same field descriptors for the four classes. But, note
that one thing you *can* do is define a "base" type that just contains the
shared fields, and then parse any of the other types as this type in order
to access the common fields. Since the field numbers match, they are
compatible.
On Sat, Jan 29, 2011 at 1:32 PM, koert <koertkuip...@gmail.com> wrote:
> I thought about these options and settled on multiple classes that all
> share a few fields. So indeed duplicate every shared field.
>
> On Jan 28, 2:28 pm, TJ Rothwell <tj.rothw...@gmail.com> wrote:
> > Is there a best practice for this use case?
> >
> > Here are some options.
> >
> > // Duplicate every field (sounds like you're doing this)
> > message FooRequest {
> > required string prompt = 1;
> > required int64 timeout = 2;
> > required Foo foo = 3;
> >
> > }
> >
> > message BarRequest {
> > required string prompt = 1;
> > required int64 timeout = 2;
> > required Bar bar = 3;
> >
> > }
> >
> > // Client code--something like this anyway
> > Foo foo = Foo.newBuilder().build();
> > FooRequest fooRequest =
> FooRequest.newBuilder().setPrompt("").setTimeout(0).
> > setFoo(foo).build();
> > Bar bar = Bar.newBuilder().build();
> > BarRequest barRequest =
> BarRequest.newBuilder().setPrompt("").setTimeout(0).
> > setBar(bar).build();
> >
> > // Share a base message and extend it
> > message BaseRequest {
> > required string prompt = 1;
> > required int64 timeout = 2;
> > extensions 1000 to max; // reserved for extensions}
> >
> > message BazRequest {
> > extends BaseRequest {
> > optional BazRequest baz = 1000;
> > }
> > required Baz baz = 1;
> >
> > }
> >
> > // Client Code
> > Baz baz = Baz.newBuilder().build();
> > BazRequest bazRequest = BazRequest.newBuilder().setBaz(baz).build();
> > BaseRequest request =
> >
> BaseRequest.newBuilder().setPrompt("").setTimeout(0).setExtension(BazRequest.baz,
> > bazRequest).build();
> > // so given a BaseRequest, how do we know if it's is a Baz or something
> > else? -- lots of hasExtension() calls? that doesn't sound good and you
> have
> > to keep track of an ExtensionRegistry if you're using a generic
> > Reader/Writer.
> > // baz is a base? not so much
> > // baz has a base? sounds right
> > // this approach doesn't seem right
> >
> > // Composition
> > message CommonRequest {
> > required string prompt = 1;
> > required int64 timeout = 2;}
> >
> > message QuxRequest {
> > required CommonRequest common = 1;
> > required Qux qux = 2;
> >
> > }
> >
> > // Client Code
> > Qux baz = Qux.newBuilder().build();
> > CommonRequest.Builder crb =
> > CommonRequest.newBuilder().setPrompt("").setTimeout(0);
> > QuxRequest bazRequest
> > = QuxRequest.newBuilder().setCommon(crb).setQux(qux).build();
> > // the challenge here would be determining how the common message is
> > defined. If you have dozens of requests that match on some fields here,
> some
> > there... it may get complicated.
> >
> > YMMV,
> > -- TJ
> >
> > On Fri, Jan 28, 2011 at 12:59 PM, koert <koertkuip...@gmail.com> wrote:
> > > i have several proto message definitions that all share the first 4
> > > fields. its as if they are all subclasses of one protobuf message
> > > format.
> > > in java can i create the FieldDescriptors for these 4 fields once and
> > > use them for the getters and setters of all these message classes? it
> > > would save me a lot in terms of logic and maybe also lead to somewhat
> > > bettter performance.
> > > best koert
> >
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