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Nothing is stopping you to define a type class
Exists:trait Exists[A] { def apply(): Boolean }
object Exists extends Nope {
implicit def sure[A](implicit a: A): Exists[A] = new Exists[A] {
def apply() = true
}
}
trait Nope {
implicit def nope[A]: Exists[A] = new Exists[A] {
def apply() = false
}
}
then you can do
def isEffect[T](implicit isIt: Exists[Effect[T]]) = isIt()
they want it at runtime
it's the same
rho issue
when
rho only had Task
it's been asked by several people several times, and still no solution :(
this is for the implementation of swagger support in rho iirc (might be wrong here)
And that's actually the other way around: I have a value and I want to see if the typeclass resolves for its runtime type, which is of course impossible in general.
It's definitely a very very niche case
I agree it's not possible, you'd need something like
TypeTag, which would need to also capture typeclass instances
trait TagHandler {
def success(x: Any): Unit
def failure(reason: Throwable): Unit
}
abstract class StandardTagHandler(val pfAllowedStates : PartialFunction[State, Unit]) extends TagHandler {
def sth_success(x : Any) : Unit
def success(x : Any) : Unit =
if (pfAllowedStates.isDefinedAt(state)) sth_success(x)
else resetToInit(s"$this called in unallowed state $state")
def failure(reason : Throwable) : Unit = {
resetToInit(s"$this failed with reason : $reason")
}
}
this is inside a FSM class that has a
state : State . i want to make this intermediate StandardTagHandlerclass so I don't keep rewriting the state check boiler plate
is this is right way to use the partialFunction? or should it be
State => Boolean check or something like that
I think the consensus is that it's not possible
it depends on what your state transitions look like. If you have
State1 <: State etc, you could have a class StateTransition[A, B], have the method that does a state transition from From to To take an implicit StateTransition[From, To], and have a bunch of implicit object transitionFromTo extends StateTransition[From, To] for the allowed transitions
those could be phantom types too
I don’t really want to write my own :smile:
Let's say I have athe following case class:
case class Person(name: String, age: Int)
@tondostefano_twitter Or lenses. I should prbably wait for you to finish :)
I mean, I oversimplified my example, but that's the core
let me show my code, perhpas it's gonna be more clear
@tondostefano_twitter Shapeless will give you a lot more stuff to work with Person as "a string and an int", etc.
def updatePhoneCallWithCodiceStatistica(guid: String, codiceStatistica: String, fieldName: String): Future[Option[Future[Int]]] =
phoneCallsDAO.findByGuid(guid).map { ph =>
ph.map { call =>
val callUpdated = call.copy(codiceStatistica = Some(codiceStatistica))
phoneCallsDAO.update(call.id.get, callUpdated)
}
}
I know it's ugly
but what I'm trying to achieve is to make the copy parameter dynamic
Are all the fields the same type?
fields type are arbitrary