<@UL0QMJ80P> - `Option.getOrElse` returns the val...

# arrow

[AdrianRaFo]

@Fred Friis
- Option.getOrElse returns the value inside if the Option is a Some or return the provided param if it's a None
- Option.orElse returns the same Option if it's not None, otherwise returns the provided Option
The difference here is that getOrElse will return the value outside the Option context but the orElse keep that context

[Fred Friis]

aah like this?

val foo = Option.just("foo")
        
        foo.orElse { "bar" } //doesn't compile, needs an alternative Option
        foo.orElse { Option.just("bar") } //alternative Option, compiles
        
        foo.getOrElse { "bar" } //if empty default value 
        foo.getOrElse { Option.just("bar") } //not idiomatic- use orElse instead

[AdrianRaFo]

yes

[AdrianRaFo]

if you changes the foo to None you will see the bar and Option(bar) respectively

[Fred Friis]

+ my understanding is none of the arrow Option methods have the dangerous problem of java 8 optional where optional.orElse() eagerly evaluates with potentially undesirable/dangerous side effects even when the optional is NOT empty, is my understanding correct?

[AdrianRaFo]

never tried java 8 optionals but if an Arrow's Option is not suspended so whatever you put inside when you are creating one will be executed eagerly. The common pattern is put the nullable thing inside and continue working with the option

[Imran/Malic]

If you want a non eager Option just use the new suspended Either constructor Either.catch

[Imran/Malic]

You may have to migrate to 0.10.0-Snapshot or wait for the stable release

[Imran/Malic]

this is how it looks like:

val someString: suspend () -> Either<Throwable, String> = suspend { Either.catch { "4" } }

[Fred Friis]

private fun getUserFromCache(userId: UserId) : Option<User> {
        return cache.getUserById(userId)
    }

    private fun getUserFromDb(userId: UserId) : Option<User> {
        return db.getUserById(userId)
    }

    fun getUser(userId: UserId) : Option<User> {
        val userFromCache = getUserFromCache(userId)
        // i don't want this expensive db call to be executed if userFromCache is Some
        // as that would defeat the purpose of returning quickly from a cache
        // but you're saying it will execute irrespective of whether userFromCache is Some or None?
        return userFromCache.orElse { getUserFromDb(userId) }
    }

[Fred Friis]

^^^ hope that's a clear way to articulate my problem?

[simon.vergauwen]

// but you’re saying it will execute irrespective of whether userFromCache is Some or None?

It will not execute if userFromCache returns Some.