Hi guys, I have a data which is coming from the server and it can be

null

or

empty

. I tried to filter basic to avoid null code and replace with

empty

1️⃣

fun filterMovieItemList(unfilteredList: List<MovieItem>): List<MovieItemModel> {
    val movieItemModelList = mutableListOf<MovieItemModel>()
    if (unfilteredList.isNotEmpty()) {
        unfilteredList.forEachIndexed { _, movieItem ->
            val movieDetails = movieItem.movieDetails
            if (movieDetails != null && !movieDetails.name.isNullOrEmpty()) {
                val icon = movieDetails.iconUrl ?: "xyz"
                movieItemModelList.add(
                    MovieItemModel(
                        movieDetails.name,
                        icon,
                        movieDetails.summary ?: "",
                    )
                )
            }
        }
    }
    return movieItemModelList
}

I would do something like this:

return unfilteredList.asSequence()
        .mapNotNull { it.movieDetails }
        .filterNot { it.name.isNullOrEmpty() }
        .map { movieDetails ->
            MovieItemModel(
                movieDetails.name.orEmpty(),
                movieDetails.iconUrl ?: "xyz",
                movieDetails.summary.orEmpty(),
            )
        }
        .toList()

As for general knowledge what is the

asSequence()

do? what are the benefits will get?

To avoid the fact that we have to account for a nullable name when it is already filtered out, I'd do:

fun filterMovieItemList(unfilteredList: List<MovieItem>): List<MovieItemModel> =
    unfilteredList.mapNotNull { it.movieDetails?.toMovieItemModelOrNull() }

fun MovieItemDetails.toMovieItemModelOrNull(): MovieItemModel? = 
    if (name.isNullOrEmpty()) {
        null 
    } else {
        MovieItemModel(
            name,
            iconUrl ?: "xyz",
            summary ?: "",
        )
    }

It transform the

List

in a

Sequence

. It's not mandatory but the difference with

List

is that, when chaining calls (.filter, .map, etc), you don't intanciate a new

List

at each step

when we convert the

List

to

Sequence

. Does it will impact on performances?

No, it just uses its iterator

perfect thanks...

1. `unfilteredList.asSequence()`: Transform the List in a Sequence 2. `.mapNotNull { it.movieDetails }`: Iterate only over movieDetails, ignore those who are null 3. `filterNot { it.name.isNullOrEmpty() }`: Ignore values (movieDetails) with null names or empty names. 4. `.map { ... }`: Convert values (movieDetails with a name) to a MovieItemModel instance 5. `.toList()`: Execute the Sequence iteration an save each items that went through all steps in a list

perfect thanks a million. I got it now...