is it possible to do something like this in kotlin...
# getting-startedy
Yusuf.I
09/25/2022, 7:12 PMis it possible to do something like this in kotlin
Copy code
interface ClientEvents {
ready: () => void;
}
export declare interface Client {
on<Event extends keyof ClientEvents>(
event: Event,
listener: ClientEvents[Event],
): this;
off<Event extends keyof ClientEvents>(
event: Event,
listener: ClientEvents[Event]
): this;
emit<Event extends keyof ClientEvents>(
event: Event,
...args: Parameters<ClientEvents[Event]>
): boolean;
}Yusuf.I
09/25/2022, 7:13 PMThis code is from type script
Yusuf.I
09/25/2022, 7:14 PMa
August Lilleaas
09/25/2022, 7:15 PMI don’t think so, there’s no structural typing in Kotlin afaik
y
Yusuf.I
09/25/2022, 7:17 PMwould there be a way to do anything similar
Yusuf.I
09/25/2022, 7:18 PMlike
Copy code
client.on<ReadyEvent> { c -> {
}Yusuf.I
09/25/2022, 7:19 PM@August Lilleaas
a
August Lilleaas
09/25/2022, 7:19 PMnot sure exactly what you’re asking, but if I understand you correctly, then yes, it’s possible to specify the types for lambda arguments 🙂
y
Yusuf.I
09/25/2022, 7:22 PMso i am trying to create an event listener system where once i want to use client.on to recieve the event
a
August Lilleaas
09/25/2022, 7:23 PMyou could create an inline extension function with a reified type for the event. That way, you can use the type of the event to run the code you want
August Lilleaas
09/25/2022, 7:24 PMso, instead of onFooEvent, onBarEvent, etc, you can use a generic type and call on<FooEvent>, on<BarEvent>, etc
y
Yusuf.I
09/25/2022, 7:24 PMah i see
Yusuf.I
09/25/2022, 7:24 PMthank you for the help
a
August Lilleaas
09/25/2022, 7:25 PM(it doesn’t have to be an extension function, by the way)
y
Yusuf.I
09/25/2022, 7:26 PMcan you give me a ruff example please
a
August Lilleaas
09/25/2022, 7:28 PMwhat are you trying to do, and what errors are you getting?
August Lilleaas
09/25/2022, 7:29 PMah, I see the problem now. The type of the event needs to define the type of the lambda
y
Yusuf.I
09/25/2022, 7:30 PMyeah
Yusuf.I
09/25/2022, 7:31 PM Copy code
inline fun <reified T : Event> EvenTester.on(
crossinline consumer: suspend EventListener.(T) -> Unit
) {
}Yusuf.I
09/25/2022, 7:31 PMdoes this look right?
a
August Lilleaas
09/25/2022, 7:36 PMyou can use typealiases for the events themselves. After all, the only thing the type needs to indicate, is the type of the lambda handlers
y
Yusuf.I
09/25/2022, 7:37 PMhow do typealiases work
a
August Lilleaas
09/25/2022, 7:41 PMactually, that won’t work, as typealiases are subject to type erasure even for reified types
y
Yusuf.I
09/25/2022, 7:42 PMoh ok
a
August Lilleaas
09/25/2022, 7:45 PMI’m not an expert, but it seems to me that the only way to do this in Kotlin is to have a function for each event type
y
Yusuf.I
09/25/2022, 7:46 PMok
Yusuf.I
09/25/2022, 7:48 PMwill try that out and let you know if it works