Are you sure that "message" is a MsgFrame class? Since dynamic_cast<>() is
failing, I suspect it is not.
You should be aware that m1->CopyFrom(m2) can succeed even if m1 and m2
have different C++ classes, as long as both classes have the same
descriptor. For example, m1 could be MsgFrame and m2 could be
DynamicMessage, and CopyFrom() will succeed. But for C++ dynamic_cast<>()
they must be the exact same class.
If you are using DynamicMessageFactory, you can probably solve this problem
by calling:
DynamicMessageFactory factory;
factory.SetDelegateToGeneratedFactory(true);
This will make DynamicMessageFactory return instances of compiled-in
classes where possible, instead of DynamicMessage.
Josh
On Wednesday, February 17, 2016 at 11:09:08 AM UTC-8, Elmar van wrote:
>
> Hello,
>
> I'm trying to have an abstract layer which delivers
> google::protobuf::Message, I assign a type by setting the descriptor.
> This all works great.
> Now I have a general callback function which has one argument, a reference
> to a protobuf message.
>
> static void receiveCallback(google::protobuf::Message &message)
>
> Now another software layer of mine uses this abstract library, this layer
> has messages defined. So I'm looking for a performant way to cast this
> reference and I'm not quite sure why it wont work.
>
> Using a dynamic_cast throws a bad cast exception, using a static_cast the
> datas are not set.
> try {
> MsgFrame & frame = dynamic_cast<MsgFrame&>(message);
> LOG(DEBUG)<<frame.number();
> } catch (const std::bad_cast& e) {
> LOG(WARNING) << e.what();
> }
>
>
> However when I create a new MsgFrame and use CopyFrom(..) it works as
> expected. But this is not wanted due to performance overhead.
>
> What is the correct way to cast it?
>
> Thanks in advance!
>
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