Kotlin Set filterIsInstanceTo()
Syntax & Examples

Set.filterIsInstanceTo() extension function

The filterIsInstanceTo() extension function in Kotlin filters elements in a set, appending all elements that are instances of the specified type or class to the given destination collection.

Syntax of Set.filterIsInstanceTo()

There are 2 variations for the syntax of Set.filterIsInstanceTo() extension function. They are:

1.
fun <R, C : MutableCollection<in R>> Set<*>.filterIsInstanceTo(destination: C): C

This extension function appends all elements that are instances of specified type parameter R to the given destination.

Returns value of type C.

2.
fun <C : MutableCollection<in R>, R> Set<*>.filterIsInstanceTo(destination: C, klass: Class<R>): C

This extension function appends all elements that are instances of specified class to the given destination.

Returns value of type C.


✐ Examples

1 Appending instances of String to a list

Using filterIsInstanceTo() to filter elements in a set that are instances of String and append them to a list.

For example,

  1. Create a set containing elements of different types.
  2. Create an empty list to hold the filtered elements.
  3. Use filterIsInstanceTo() to filter elements that are instances of String and append them to the list.
  4. Print the resulting list.

Kotlin Program

fun main(args: Array<String>) {
    val mixedSet: Set<Any> = setOf(1, "two", 3.0, "four", 5)
    val stringList = mutableListOf<String>()
    mixedSet.filterIsInstanceTo(stringList)
    println(stringList)
}

Output

["two", "four"]

2 Appending instances of Int to a set

Using filterIsInstanceTo() to filter elements in a set that are instances of Int and append them to another set.

For example,

  1. Create a set containing elements of different types.
  2. Create an empty set to hold the filtered elements.
  3. Use filterIsInstanceTo() to filter elements that are instances of Int and append them to the new set.
  4. Print the resulting set.

Kotlin Program

fun main(args: Array<String>) {
    val mixedSet: Set<Any> = setOf(1, "two", 3.0, 4, 5)
    val intSet = mutableSetOf<Int>()
    mixedSet.filterIsInstanceTo(intSet)
    println(intSet)
}

Output

[1, 4, 5]

3 Appending instances of Double to a list

Using filterIsInstanceTo() to filter elements in a set that are instances of Double and append them to a list.

For example,

  1. Create a set containing elements of different types.
  2. Create an empty list to hold the filtered elements.
  3. Use filterIsInstanceTo() to filter elements that are instances of Double and append them to the list.
  4. Print the resulting list.

Kotlin Program

fun main(args: Array<String>) {
    val mixedSet: Set<Any> = setOf(1, "two", 3.0, 4, 5)
    val doubleList = mutableListOf<Double>()
    mixedSet.filterIsInstanceTo(doubleList)
    println(doubleList)
}

Output

[3.0]

Summary

In this Kotlin tutorial, we learned about filterIsInstanceTo() extension function of Set: the syntax and few working examples with output and detailed explanation for each example.