> Neither. Return a blocking iterator, something like
>
> type Iterator struct {
> // Next blocks until a new message is available or the stream ends and
> returns if a new message is available.
> Next() bool
> // Message returns the current message. Must only be called after Next
> returns true.
> Message() []byte
> // Error returns the error reading the next message, if any.
> Error() err
> }
>
> and let the user use their own channels/goroutines, if they need it.
>
> That is what I would consider idiomatic Go. I would not consider it
> idiomatic to return/accept channels as part of your API anymore.
>
I definitely agree with Axel on the blocking / non-blocking thing.
Digressing from the main point, but it may be more idiomatic to just return
a concrete type, like *mqtt.Reader or *mqtt.Connection (if your package
name is "mqtt"). The concrete type will have the iterator methods, plus any
others for MQTT-specific stuff. For example:
reader, err := mqtt.Dial("url") // reader is type *mqtt.Reader
if err != nil { ... }
for reader.Next() {
msg, err := reader.Message()
if err != nil { ... }
}
if reader.Err() != nil { ... }
The reason is that then it's easy for callers to call MQTT-specific methods
on the concrete type as well. In parts of the program that *take* a message
reader, however, you'll probably use a locally-defined interface with just
the methods you need. If the mqtt package defines the interface, it'll
invariably include more methods than most people need.
Other considerations:
* Perhaps call the error method just Err(). That's common, for example,
bufio.Scanner.Err.
* Maybe make mqtt.Reader.Message() return an mqtt.Message struct, which has
Bytes() and Text() methods, as well as other MQTT message-specific stuff
(topic, message ID, etc).
-Ben
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