On Thu, Oct 1, 2009 at 3:39 AM, Carlo Medas <[email protected]> wrote:
> I would like to manually enumerate the available extensions to my
> RpcMessage. This is easily done by using an ExtensionFactory in Java
> code.
>
What's ExtensionFactory? Do you mean ExtensionRegistry? But it doesn't
allow you to enumerate extensions, only search for specific ones.
> In C++ it's not there, so we tried to use the
> google::protobuf::Descriptor, but neither the extension_count and
> field_count keep track of the created extensions.
>
extension_count keeps track of extensions declared within the message's
scope. E.g. I can do:
message Foo {
extend Bar {
optional int32 baz = 1;
}
}
Here, "baz" is declared within Foo's scope, even though it is extending Bar.
My guess is that you want to know all the extensions which are extending
your Descriptor, not all of the extensions declared within the scope of your
Descriptor. In that case, you have two options:
1) DescriptorPool (which you can get using descriptor->file()->pool()) has
methods for searching for extensions.
2) The Reflection interface for a particular message (returned by
message.GetReflection()) has methods for searching for extensions.
However, like in Java, you can not iterate over all known extensions. You
can only search for particular ones.
> Pretending that I managed to know the field assigned to that
> extension, the following code is going to work in order to assing the
> value to that extension field by using reflection?
>
> const google::protobuf::Reflection* reflection =
> rpcMessage.GetReflection();
> google::protobuf::Message* msg = reflection->MutableMessage
> (&rpcMessage, field);
> msg->CopyFrom(*response);
>
Yes. The reflection interface treats regular fields and extensions exactly
the same.
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