Hi,
Related to this, I tried the following schema:
interface MyType {
getName @0 () -> (name :Text);
}
struct ObjectInfo {
object @0 :MyType;
isA @1 :Bool;
}
interface Test {
getObjectInfo @0 () -> (objectInfo: ObjectInfo);
}
After generating the C++ classes, on the client side, there is a
getObject() method implemented on the ObjectInfo class but no getIsA().
auto request = testClient.getObjectInfoRequest();
auto promise = request.send();
auto objectInfo = promise.getObjectInfo();
auto object = objectInfo.getObject();
bool isA = objectInfo.getIsA(); //not implemented
Is it because of the Bool type ?
Thanks !
Christophe
Le samedi 8 octobre 2022 à 15:26:42 UTC+2, Christophe Alexandre a écrit :
> Thanks a lot for your very clear answer.
>
> Christophe
>
> Le vendredi 7 octobre 2022 à 22:42:04 UTC+2, ken...@cloudflare.com a
> écrit :
>
>> Hi Christophe,
>>
>> There is no built-in mechanism for this. Instead, you have to build this
>> into your interface.
>>
>> Note that a `Client` object can be "safely" cast to any type using
>> `client.castAs<SomeInterfaceType>()`. I say "safely" meaning: you won't
>> violate C++ memory safety by this cast, even if the server doesn't actually
>> implement the type. Instead, if you cast to the wrong type, method calls on
>> that type will fail with UNIMPLEMENTED exceptions. The exception is
>> produced on the server side; the client side does not actually know the
>> destination type so cannot predict whether the method is supported.
>>
>> To that end, one way to query the type would be to simply try to call a
>> method on `ConcreteA` or `ConcreteB` and see if it fails with
>> `exception.getType() == kj::Exception::Type::UNIMPLEMENTED`.
>>
>> But if you'd like to avoid the round trip, then I would suggest that
>> `getAbstracts()` should return a list that contains not just the interface
>> pointers, but also associated metadata identifying what type it is.
>>
>> -Kenton
>>
>> On Fri, Oct 7, 2022 at 5:05 AM Christophe Alexandre <
>> christophe...@zellij.io> wrote:
>>
>>> Hi,
>>> Sorry for the newbie question.
>>>
>>> I've read the following thread and this is related to the same kind of
>>> question.
>>> https://groups.google.com/g/capnproto/c/XLo5RPLpVBg/m/LI_sGi72AgAJ
>>>
>>> With following schema example:
>>> interface Abstract {}
>>> interface ConcreteA extends(Abstract) {}
>>> interface ConcreteB extends(Abstract) {}
>>> interface Object {
>>> getAbstracts @0 () -> (abstracts :List(Abstract));
>>> }
>>>
>>> When implementing getAbstracts on the server side, only ConcreteA or
>>> ConcreteB objects are constructed and returned.
>>> My question is: on the client side, what is the best practice for
>>> determining the Abstract object concrete type and casting it to ConcreteA
>>> or ConcreteB. Something equivalent to C++ dynamic_cast.
>>>
>>> Thanks !
>>> Christophe Alexandre
>>>
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>>>
>>
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