How do you make a cast in a databinding expression?

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I have a sealed class which is being sending via StateFlow. How to cast it in order to retrieve an enclosed value? I cannot find any example of syntax for databinding expressions.

dataclass UserInfo(val name: String)

sealed class ResultOf<out T> {
  data class Success<out R>(val content: R): ResultOf<R>()
  data class Failure(val throwable: Throwable): ResultOf<Nothing>()
}

val model = ResultOf.Success.content(UserInfo("John Doe"))

<variable
            name = "viewModel"
            type="com.example.hello.user.ResultOf"/>

<TextView
    android:id="@+id/name"
    android:text="@{ ??? }"
/>

viewModel.Success.content.name

(UserInfo)viewModel.content.name

(viewModel as UserInfo).content.name

None of the above works neither

android-databinding kotlin android-layout android
1 Answers

Not sure if there is a way to go about this using casting in a conditional statement in XML at the moment.

You could go about this by creating a BindingAdapter. Like so:

data class User(val name: String)

sealed class ResultOf<out T: Any> {
    data class Success<out R: Any>(val content: R): ResultOf<R>()
    data class Failure(val throwable: Throwable): ResultOf<Nothing>()
}

The BindingAdapter:

@BindingAdapter("app:userName")
fun TextView.setUserName(result: ResultOf<User>) {
    text = when(result) {
        is ResultOf.Success -> result.content.name
        is ResultOf.Failure -> ""
    }
}

Layout file:

<data>
    <import type="com.example.hello.user.ResultOf" />
    <import type="com.example.hello.user.User" />

    <variable
        name="userResult"
        type="ResultOf&lt;User>" />
</data>

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:userName="@{userResult}"/>
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