Sampling a behaviour from outside network

Question

Since sodium has been deprecated by the author I'm trying to port my code to reactive-banana. However, there seem to be some incongruencies between the two that I'm having a hard time overcomming.

For example, in sodium it was easy to retrieve the current value of a behaviour:

retrieve :: Behaviour a -> IO a
retrieve b = sync $ sample b

I don't see how to do this in reactive-banana

(The reason I want this is because I'm trying to export the behaviour as a dbus property. Properties can be queried from other dbus clients)

Edit: Replaced the word "poll" as it was misleading

Answer 1

If you have a Behaviour modelling the value of your property, and you have an Event modelling the incoming requests for the property's value, then you can just use (<@) :: Behavior b -> Event a -> Event b¹ to get a new event occurring at the times of your incoming requests with the value the property has at that time). Then you can transform that into the actual IO actions you need to take to reply to the request and use reactimate as usual.

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¹https://hackage.haskell.org/package/reactive-banana-1.1.0.0/docs/Reactive-Banana-Combinators.html#v:-60--64-