How would you guys model the one_of feature described
[here](https://developers.google.com/protocol-buffers/docs/proto3#oneof) in nim?
I was thinking along these lines: Given the proto file:
message ConformanceRequest {
oneof payload {
bytes protobuf_payload = 1;
string json_payload = 2;
}
WireFormat requested_output_format = 3;
}
Compile it to the following nim file:
PbMessage ConformanceRequest*:
PbOneOf payload:
protobuf_payload: PbBytes @1
json_payload: PbString @2
requested_output_format: WireFormat @3
And then let the macros then expand to something like:
type
ConformanceRequest_payload_enum = enum
not_set = 0,
protobuf_payload,
json_payload
type
ConformanceRequest_payload_inner {.union.} = object
protobuf_payload: seq[uint8]
json_payload: string
type
ConformanceRequest_payload = object
kind: ConformanceRequest_payload_enum
inner: ConformanceRequest_payload_inner
type
ConformanceRequest = object
payload: ConformanceRequest_payload
requested_output_format: WireFormat
# some `.` overload on ConformanceRequest_payload to set the kind according
to which payload you set
# not sure if `.` overload can see if it is used as getter or setter
And then use it like:
var cr : ConformanceRequest
assert(cr.payload.kind == not_set)
cr.payload.json_payload = "Hello"
assert(cr.payload.kind == json_payload)
I'm not really sure of the usage of the Kind enum is idiomatic nim style and
also the manual says the union pragma doesn't support garbage collected values,
so I guess the seq and string are off limits?
The C++ implementation generates a bunch of has_xxx() and set_xxx() functions,
but I think that is pretty ugly, nim should do better right?
