Hi everyone, I'm trying to remove a duplication of this code: ```.filter { _key, value -> ...

# announcements

[Alessandro Tagliapietra]

Hi everyone, I'm trying to remove a duplication of this code:

.filter { _key, value ->
            value.getTimestamp().isBefore(Instant.now().plusSeconds(600))
        }

key is a string but I don't care what type it is
value can be multiple types but all implement the getTimestamp method that returns an instant, so I've tried tried to create a file like this:

interface DataWIthTimestamp {
    fun getTimestamp(): Instant
}

val filterFutureData: (key: Any, value: DataWIthTimestamp) -> Boolean = { _, value ->
    value.getTimestamp().isBefore(Instant.now().plusSeconds(600))
}

which doesn't work as it says

Type mismatch.
Required: Predicate<in String!, in Metric!>!
Found: (Any, DataWIthTimestamp) → Boolean

I know my implementation might not make sense 🙂

[Nir]

In order to make this work the way you'd want, for starters, you'd need to have some common interface that specifies getTimestamp

[Nir]

that all the types you want it to work with, implement

[Nir]

value can be multiple types but all implement the getTimestamp method that returns an instant, so I've tried tried to create a file like this:

fkjdf

[Nir]

arg

[Nir]

Anyhow, the point is Kotlin cannot do anything with that information unless you either a) implement the function for every single type value can be, or b) all of those types inherit from some common interface

[Alessandro Tagliapietra]

Oh, so they have to specifically implement that interface? just because those types are generated by avro and outside of my control

[Nir]

Right, so if those types are out of your control and don't implement an interface, then the best you can do is to factor out the rest of it into a function

[Alessandro Tagliapietra]

a) is there, all those types I'll use the predicate in will implement the getTimestamp method

[Alessandro Tagliapietra]

I've created the interface just to use it in the filterFutureData predicate

[Nir]

No, I mean you need to implement filterFutureDate

[Nir]

separately

[Nir]

for every type

[Nir]

unless they have a common base

[Nir]

Either that or maybe do some reflection god-awful stuff but you probably don't want to do that

[Alessandro Tagliapietra]

oh ok got it, so that'll still make me write that predicate once per type

[Nir]

yeah

[Alessandro Tagliapietra]

thanks for helping @Nir I think I'll just use it directly as I only use it once per type

[Nir]

I don't know all your circumstances but I'd guess that what makes sense, assuming they all use the same timestamp type

[Nir]

is to just factor out hte function starting from that point

[Nir]

fun filterFutureDate(value: Timestamp) = value.isBefore(Istant.now().plusSeconds(600))

[Nir]

and now you could at least do

.filter { _, value -> filterFutureDate(value.getTimestamp()) }

[Nir]

or maybe write it as an extension function on timestamp instead, so you can write value.getTimestamp().filterFutureDate()

[Nir]

etc

[Alessandro Tagliapietra]

oh ok that might be doable too, thanks a lot!