Any one please explain this code. Thanks

# announcements

[Mohammad Jahidul Islam]

Any one please explain this code. Thanks

[Roukanken]

what do you don't understand?
(also would be great if you posted the code directly next time...)

[Stephan Schroeder]

improvement: since the code assumes that the Success.data should be non-null in order for the Result to count as succeeded, the generic type should be restricted to (non-nullable) Any :

data class Success<T:Any>...

[Stephan Schroeder]

I fixed it for you

sealed class Result<R:Any> {
    data class Success<R:Any>(val data: R): Result<R>()
    data class Error(val exception: Exception): Result<Nothing>()
}

val Result<*>.succeeded get():Boolean = this is Result.Success

fun <T:Any> Result<T>.successOr(fallback: T): T = when(this) {
    is Result.Success -> this.data
    else -> fallback
}

So basically you have a sealed class with an extension property and and extension method. Those two could definitely have been defined inside of Result directly but this way it's easier to see what Result is all (/mostly) about.
• it's debatable if you still need succeeded since result.succeeded is only a shorthand for result is Result.Success which would come with a smart-cast

[Stephan Schroeder]

Nothing is the type on Error, because Error doesn't come with any instance of R . It's a bit of an advanced concept, but Nothing is assignable to all (non-nullable) types since it doesn't exist anyway to cause troubles at runtime.
It's very elegant once you wrap your head around it.