ably
Json messages are not decoded transparently
When a struct is sent over a channel it is turned to json. Then when it is received on the other end it is meant to be transparently turned back to that struct. Instead, a json string is received.
However this works correctly when using the history API. This means the messages are being correctly sent but not received.
The history code also converts to a generic map instead of the struct. Both should be changed to return the struct.
Clients may rely on this bad behaviour so this change will need to be for v2.
┆Issue is synchronized with this Jira Task by Unito
The history code also converts to a generic map instead of the struct. Both should be changed to return the struct.
I think this will need some form of struct registration, because the SDK won't be able to infer which in-memory struct to decode into without being told about it.
It may be worth considering a Message.Decode(dst interface{}) method which decodes msg.Data into the provided object:
channel.Subscribe(ctx, func(msg *ably.Message) {
var data MyStruct
if err := msg.Decode(&data); err != nil {
return
}
// do something with data
})
Longer term we'd like to have first class support for schemas (e.g. register a protobuf definition for a channel, and the SDK decodes messages based on that definition).
It may be worth considering a
Message.Decode(dst interface{})method
This is a wider question than just for this library and should be discussed as such. @QuintinWillison
