Hi, I have a requirement to make use of two typeclasses `Async<F>, ApplicativeError<S, Nel&...

# arrow

[Gopal S Akshintala]

Hi, I have a requirement to make use of two typeclasses Async<F>, ApplicativeError<S, Nel<E>>. I achieved it as below:

interface RepoTC<F> : Async<F> {
    fun User.isUserCityValid(): Kind<F, Boolean>

    fun <S> ApplicativeError<S, Nel<ValidationError>>.userCityShouldBeValid(user: User) = fx.async {
        val cityValid = user.isUserCityValid().bind()
        if (cityValid) [e-mail](cityValid)
        else raiseError(UserCityInvalid(user.city).nel())
    }
}

But it just doesn’t feel right, as:
- It can’t be extended if I need other typeclasses.
- I see ApplicativeError in Async hierarchy. So do I need both the TCs?

I tried this, but am getting compiler errors due to clashes.

interface RepoTC2<F, S> : Async<F>, ApplicativeError<S, Nel<ValidationError>> {
    fun User.isUserCityValid(): Kind<F, Boolean>

    fun userCityShouldBeValid(user: User) = fx.async {
        val cityValid = user.isUserCityValid().bind()
        if (cityValid) just(cityValid)
        else raiseError(UserCityInvalid(user.city).nel())
    }
}

Can I achieve it just by using Async itself?

[raulraja]

in meta you’d get them auto injected but in this case currently the alternative is to use them as abstract functions in the interface or properties

[raulraja]

since they subtype each other but the types they target are different F and S

[Gopal S Akshintala]

Thanks @raulraja, can u pls elaborate “alternative is to use them as abstract functions in the interface or properties”

[raulraja]

don;t extend them but instead use them as properties or inject them via constructor as dependencies

[Gopal S Akshintala]

oh ok

[Gopal S Akshintala]

got it

[raulraja]

then you may use TC.run { }

[raulraja]

if you want a block with the syntax of any of them

[Gopal S Akshintala]

Sure, I shall try it out and get back

[Gopal S Akshintala]

Thanks @pakoito! Will try it out