is there something like `val myVar by lazy{ something() }`, but does not cache the value, but re-eva...

# getting-started

[Xad Kile]

is there something like val myVar by lazy{ something() }, but does not cache the value, but re-evaluates the value every time myVar it is access? myVar is a local variable

[ephemient]

val myVar
    get() = something()

[Xad Kile]

@ephemient excuse me, I should have been clearer. In my case myVar is a local variable. Is there a built-in for that? Thank you

[ephemient]

val myVar by ReadOnlyProperty { _, _ -> something() }

[ephemient]

you could write your own extension

operator fun <T> (() -> T).getValue(thisRef: Any?, property: KProperty<*>): T = invoke()

which would allow you to write

val myVar by { something() }

[gildor]

why having myVar for this at all? can it be just always call something()
I feel that it shows intent and behaviour better and would cause unexpected results like:
if (myVar == anotherVar || myVar == oneMoreVar)

[Xad Kile]

@ephemient thank you so much 😄
@gildor I am trying out kotest. There is this lateinit var var1. On JUnit I would just use get() to make shortcut to `var1`'s properties, but since this is kotest, everything is stored inside a lambda and get() can't be applied to local variables, and I don't want to repeat var1.p1 . It looks something like this:

KotestLambda {
    lateinit var var1:Any
    val p1 by myDelegate{var1.p1}
    beforeTest{
        var1 = initVar1()
    }
    test("test 1"){
        // p1 is accessed multiple times.
    }
}

[gildor]

I don’t want to repeat var1.p1

Personal opinion, I would rather repeat it instead of introducing additional property for this

Ehh, this lateinit is really nasty 🙈

// p1 is accessed multiple times.

Can you just declare local p1 on test 1 level?

[Xad Kile]

@gildor how is that lateinit nasty? I would like to know more.
Of course I can declare it in test 1, but it is also used in many other tests. So, after typing this out for like 20 times, I thought I should make a shortcut.

[gildor]

I don’t say that there is a much better solution, I’m not really into this style of testing, but I would expect that just every test calls initVar1() instead of using lateinit

[gildor]

in general I feel that lateinit is always a band-aid for some not very nice interaction
Don’t say that I don’t do the same, just feel every time that I (or language, or library which I use) failed %)

[Xad Kile]

@gildor yes, I fell the same when I saw lateinit is in Hilt example code. It's always the final solution. Maybe I'm just too lazy here 😅. Thanks for the insight thought

[gildor]

Hilt is different story (somewhat) that you cannot use constructor injection for things like Activity/Fragment, so yes, it’s the case when Language + Framework (Android) + DI injection library all failed a bit with this interaction, so you have to use lateinit (though way how Android creates Activities is the main reason)
So this why limit usage of it to 1-2 properties per activity to inject only something like ViewModel is way to fight with it

[Xad Kile]

absolutely

[gildor]

Still, why you cannot just do:

test("test 1") {
   val p1 = initVar1().p1
}

[Xad Kile]

same old story, i don't want to repeat writing that. My app is fairly large, and there are a lot of tests (a lot, a lot) in it, repeating just a single line become a real issues. So I put the initVar1() into beforeTest, and make p1 the shortcut.

[ephemient]

as a tangent, https://developer.android.com/reference/android/app/AppComponentFactory can enable class MyActivity @Inject constructor(...) etc. on Android 9+, and somebody sufficient motivated could use AsmClassVisitorFactory to bring that to older APIs. but that's pretty far astray from this topic :)

[gildor]

Yep, aware about this API
Also that it’s already possible with Fragments, but still, it’s not very practical for Activity, looks that attempt to solve lateinit with bytecode manipulation is case when cure worse than the disease