Kotlin: Filtering a list return the original list if no match found

user_10425982 0
Viewed 873

I want an inline function that filters through a list and returns the original list if there is no match rather than returning null

I have this feature that filters through the list and returns the filtered list or empty

fun List<Obj>?.filterQueryText(queryText : String?) = this?.filter {
    queryText.equals(it.objName)
}.orEmpty()

How do I make it so that it will return to the original list if no match is found in the query?

kotlin
2 Answers

This should do the trick

fun List<Obj>?.filterQueryText(queryText : String?) = this?.filter {
    queryText.equals(it.objName)
}?.run {if (isEmpty()) this@filterQueryText else this}.orEmpty()

see it in action here

user_15148610

Generic filter for List<T>:

fun <T> List<T>?.filterOrOriginal(predicate: (T) -> Boolean) : List<T>? =
    this?.filter(predicate).takeUnless { it.isNullOrEmpty() } ?: this

Specific filter for List<Obj>:

fun List<Obj>?.filterQueryTextOrOriginal(queryText : String?) : List<Obj>? =
    this?.filterOrOriginal { queryText == it.objName }
user_139686730
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