```when (result) { Result.Loading -> {} ...

# announcements

[K Merle]

when (result) {
    Result.Loading -> {}
    is Result.Success -> SomeScreen(data= (dataResult as Result.Success<List<SomeData>>).value)
    is Result.Error -> {}
}

How do I prevent casting type on Success?

My Result class

sealed class Result<out T> {
    object Loading : Result<Nothing>()
    data class Error(val message: String) : Result<Nothing>()
    data class Success<T>(val value: T) : Result<T>()
}

[Ivan Pavlov]

If your result variable has type Result<List<SomeData>> it works as you expect
https://pl.kotl.in/FK3qHAXQD

[K Merle]

I get:

Smart cast to 'Result.Success<List<SomeData>>' is impossible, because 'result' is a property that has open or custom getter

I am using flow from ViewModel to get the state in compose.

[Ivan Pavlov]

I guess you can save your variable into a local one so that compiler can smart cast it

val resultLocal = result
when(resultLocal) {
  //use resultLocal
}

[K Merle]

Yep, that works. Why does this happen? Can I avoid it?

[Ivan Pavlov]

That's a correct behavior from the compiler perspective. Property which is open can be overridden and custom getter may produce different result on each invocation so you can't rely on it in such cases

[K Merle]

Thanks Ivan

[mcpiroman]

You may also do

when(val resultLocal = result) {
  //use resultLocal
}

[iamthevoid]

In your original post i see result in when parentheses, but when you cast - you cast dataResult

[iamthevoid]

Smartcast works for when parentheses content

[K Merle]

I changed values, sry, was not consistent

[K Merle]

@mcpiroman solution works

[iamthevoid]

Note that you can write first line of when cases as Result.Loading -> {} also as is Result.Loading -> {} . In first case works equals , in second instanceof . First case only possible for object classes