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capnproto / go-capnp

Cap'n Proto library and code generator for Go
https://capnproto.org
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Implementing multiple disjoint interfaces is awkward #86

Closed zenhack closed 7 years ago

zenhack commented 7 years ago

So, I just tripped over a problem I don't know how to solve cleanly with the current capnproto APIs: Sandstorm defines an interface AppPersistent in grain.capnp. It's disjoint from any other type heirarchy. Any object that is to be shared with other grains must implement this. But, the _ServerToClient functions only export the methods for that particular type. This means that if I want to fulfill a powerbox request, I need to have a declared common subtype between the interface I actually want to export and the AppPersistent interface. I ended up declaring a bunch of stubs in this patch, but I'm rather unhappy about it.

It would be nice if there was a better way to do this -- it's very unidiomatic Go, and nothing about the protocol requires it.

zombiezen commented 7 years ago

There is a way right now, but it is subtle. If you use the _Methods generated function, you can accumulate a bunch of methods in a slice and pass that to server.New.

zenhack commented 7 years ago

This was helpful thanks. Would be nice to have a smoother way to do this, but I'd have to think a bit to come up with something.