``` inline fun lt reified T gt Config xAxis block T gt Unit kotlinlang #announcements

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Title

b

BMG

10/11/2018, 8:10 AM

inline fun <reified T> Config.xAxis(block: T.() -> Unit, axisType: AxisType) {
   xAxis = when (T::class.java) {
       NumericAxis::class.java -> {
         NumericAxis().apply(block)
       }
       else -> throw UnsupportedOperationException("currently unsupported")
   }
}

Why does it not compile? Any thoughts?

m

marstran

10/11/2018, 8:11 AM

What's the compile error?

What is the type of

xAxis

?

a

arekolek

10/11/2018, 8:23 AM

it compiles if I do:

xAxis = when (T::class) {
        NumericAxis::class -> NumericAxis().also { block(it as T) }
        else -> throw UnsupportedOperationException("currently unsupported")
    }

👍 3

b

BMG

10/11/2018, 8:25 AM

@marstran

xAxis

is a DSL function. Usage is like,

xAxis<NumericAxis> {
}

@arekolek So

block

does not take any parameter. It has receiver type

which comes from DSL usage. We did,

fun <T> Config.xAxis(block: T.() -> Unit, axisType: AxisType) {
    xAxis = when (axisType) {
        AxisType.NUMERIC -> NumericAxis().apply(block as NumericAxis.() -> Unit)
        else -> throw UnsupportedOperationException("currently unsupported")
    }
}

But looking to avoid casting.

m

marstran

10/11/2018, 8:32 AM

@BMG But your doing

xAxis = when(axisType) { .... }

. You can't assign anything to a function.

a

arekolek

10/11/2018, 8:32 AM

it could be a property of

Config

that’s what I assumed

g

gergo

10/11/2018, 8:32 AM

not sure if you can avoid casting: https://stackoverflow.com/questions/38858672/kotlin-reified-type-parameter-doesnt-smart-cast

b

BMG

10/11/2018, 8:34 AM

@marstran Ah sorry, I did not clarify.

xAxis

inside that function is a property of type

Axis

.

@arekolek Just got it to work with your code. Thanks!

👍 1

a

arekolek

10/11/2018, 9:00 AM

@BMG and regarding

block

having a receiver instead of parameter, see my related question here https://kotlinlang.slack.com/archives/C0B8MA7FA/p1504173358000320?thread_ts=1504173358.000320

:kotlin: 1

b

BMG

10/11/2018, 9:19 AM

@arekolek Nice! I was pleasantly surprised when it worked. TIL for me 🙂

s

Sam

10/11/2018, 2:52 PM

There is a similar parameter usage in Android KTX as well

inline fun <reified T : ViewGroup.LayoutParams> View.updateLayoutParams(block: T.() -> Unit) {
    val params = layoutParams as T
    block(params)
    layoutParams = params
}

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