Does anyone know how to make something like this :...

# announcements

[Nowak]

Does anyone know how to make something like this 🙂 ? I want to have type hints for reaction based on T class extended DomainEvent.

val chainReactions: ChainReactions = mutableMapOf()
typealias ChainReactions = MutableMap<DomainEvent, DomainEvent>

[rocketraman]

reaction is a lambda, but you seem to be treating it as a DomainEvent? Not sure what you're trying to do here...

[rocketraman]

Not sure if its what you're looking for but doing reaction(event) will solve your compile error.

[bartvh]

(T: D) -> E is not assignable to (D) -> E because, assuming that another type Y extends D, a function of type (D) -> E must accept a Y argument, which (T) -> E does not.

[bartvh]

In this case I would just do:

chainReactions[event] = { d ->
   @Suppress("UNCHECKED_CAST")
   reaction(d as T)
}

assuming that chainReactions is encapsulated enough that the cast is guaranteed to be safe at runtime.

[bartvh]

Also, if this is your real code, I believe you can omit the E parameter altogether, and replace references to it simply with DomainEvent.

[bartvh]

Is it though? Because why is this function inline and using reified?

[bartvh]

It would be nice to have a type system that can express map value types with some relation to the type of their specific key, but that doesn't exist (yet) 🙂

[Nowak]

Of course. It was very late, I thing 🙂 The question was stupid 😛
I wanted to do something like this, of course:

fun <T : DomainEvent> chainReaction(event: T, reaction: (T) -> DomainEvent) = apply {
        this.chainReactions[event] = reaction(event)
    }