``` inline fun <reified T> Config.xAxis(bloc...

# announcements

[BMG]

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?

[marstran]

What's the compile error?

[marstran]

What is the type of xAxis?

[arekolek]

it compiles if I do:

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

[BMG]

@marstran xAxis is a DSL function. Usage is like,

xAxis<NumericAxis> {
}

[BMG]

@arekolek So block does not take any parameter. It has receiver type T 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.

[marstran]

@BMG But your doing xAxis = when(axisType) { .... }. You can't assign anything to a function.

[arekolek]

it could be a property of Config

[arekolek]

that’s what I assumed

[gergo]

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

[BMG]

@marstran Ah sorry, I did not clarify. xAxis inside that function is a property of type Axis.

[BMG]

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

[arekolek]

@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

[BMG]

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

[Sam]

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
}