StrictSignal.map returns Signal instead of StrictSignal

[ivan-klass]

val myVar = Var(42)


def myFunc(ss: StrictSignal[Int]) = ???

myFunc(myVar.signal) // ok
myFunc(myVar.signal.map(_ * 2)) // compile error

[raquo]

Yes, we'll have that eventually. We already have the mechanism to implement this, main issue is that I want to make other map-like operators like mapSome to work similarly, but that's a lot bigger task, as I need to figure out a new abstraction to implement that without massive repetition.

So I was planning to do that in 18.0, but if my schedule allows, I could add just the strict map to 17.2, and the rest later.

This was previously mentioned in #119 but I guess it's good to have a separate issue now that zoomLazy itself is done.

[ivan-klass]

@raquo thank you. I've end up with the following work-around. Not sure it's fully safe but it works.

type Cleanup = Modifier[Base]
extension [A](ss: StrictSignal[A])
  def strictMapped[B](f: A => B): (StrictSignal[B], Cleanup) =
    val mVar = Var(f(ss.now()))
    val owner = new ManualOwner
    ss.map(f).addObserver(mVar.writer)(using owner)
    (mVar.signal, onUnmountCallback(_ => owner.killSubscriptions()))

used like

def myFunc(ss: StrictSignal[Int]): HtmlElement = ???

val myVar = Var(42)
val (strictMappedSignal, cleanUp) = myVar.signal.strictMapped(_ * 2)

div(
  myFunc(strictMappedSignal),
  cleanUp
)

[raquo]

If you want a workaround for now, just make your extension method instantiate and return a LazyStrictSignal. See how Var.zoomLazy method does it.

…

On Sat, Nov 30, 2024, 7:37 AM Ivan Klass ***@***.***> wrote: @raquo <https://github.com/raquo> thank you. I've end up with the following work-around. Not sure it's fully safe but it works. type Cleanup = Modifier[Base]extension [A](ss: StrictSignal[A]) def strictMapped[B](f: A => B): (StrictSignal[B], Cleanup) = val mVar = Var(f(ss.now())) val owner = new ManualOwner ss.map(f).addObserver(mVar.writer)(using owner) (mVar.signal, onUnmountCallback(_ => owner.killSubscriptions())) used like def myFunc(ss: StrictSignal[Int]): HtmlElement = ??? val myVar = Var(42)val (strictMappedSignal, cleanUp) = myVar.signal.strictMapped(_ * 2) div( myFunc(strictMappedSignal), cleanUp ) — Reply to this email directly, view it on GitHub <#134 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAECBME34DR3ZVOPVFHRSHL2DHLUPAVCNFSM6AAAAABSXICYR2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMBZGAYTAOBRGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[raquo]

Implemented in 17.2.0 as mapLazy. Can't really change map return type of an open trait without a major release.

A future major version will expand this to more operators, but I can't really create an issue for that yet because I'm not yet sure how it should look technically. I plan to look into that in the coming months.