Given the following types:
type Event interface{}
type ActionResultEvent struct {
Result string
}
type ActionSuccessEvent ActionResultEvent
type ActionFailureEvent ActionResultEvent
type eventHandleFunc func(e Event)
My goal is to have event handlers (of type eventHandleFunc) for the concrete types ActionSuccessEvent, ActionFailureEvent, as well as for the more abstract ActionResultEvent. The latter I would like to use for both ActionSuccessEvents and ActionFailureEvents.
Now my idea was to just type cast the Event interface to the structure I would like to work on and that works nicely for the concrete types.
// Working perfectly fine
func(e Event) {
event := e.(ActionFailureEvent)
fmt.Println(event.Result)
} (ActionFailureEvent{ Result: "failure" })
func(e Event) {
event := e.(ActionSuccessEvent)
fmt.Println(event.Result)
} (ActionSuccessEvent{ Result: "success" })
Now what about handlers accepting ActionResultEvents? My absolute favourite would look like this one:
func(e Event) {
event := e.(ActionResultEvent)
fmt.Println(event.Result)
} (ActionSuccessEvent{ Result: "success" })
This obviously panics as e was of type ActionSuccessEvent.
Then we can of course cast to the initial type and back to intermediate:
// Works but would that would need to change whenever new types "extending"
// ActionResultEvent are added
func(e Event) {
var resultEvent ActionResultEvent
switch e.(type) {
case ActionSuccessEvent:
resultEvent = ActionResultEvent(e.(ActionSuccessEvent))
case ActionFailureEvent:
resultEvent = ActionResultEvent(e.(ActionFailureEvent))
}
fmt.Println(resultEvent.Result)
} (ActionSuccessEvent{ Result: "success" })
Another really nice approach from my point would be:
// Error: use of e.(type) outside type switch
func(e Event) {
resultEvent := ActionResultEvent(e.(type))
} (ActionSuccessEvent{ Result: "success" })
Can anybody think of a smooth solution? One side note: I am happy if the handler panics during runtime whenever a typecast fails, as the wrapper will recover from that.
This is the example code above on the playground. Thanks!
