Kotlin 지도 컬렉션 – map() 메서드

I. map() 메서드를 사용한 Kotlin 지도 컬렉션

1. fun <K, V, R> Map<out K, V>.map(transform: (Map.Entry<K, V>) -> R): List<R>
2. fun <K, V, R : Any> Map<out K, V>.mapNotNull(transform: (Map.Entry<K, V>) -> R?): List<R>
3. fun <K, V, R, C : MutableCollection<in R>> Map<out K, V>.mapTo(destination: C, transform: (Map.Entry<K, V>) -> R): C
4. fun <K, V, R : Any, C : MutableCollection<in R>> Map<out K, V>.mapNotNullTo(destination: C, transform: (Map.Entry<K, V>) -> R?): C
5. fun <K, V, R> Map<out K, V>.mapKeys(transform: (Map.Entry<K, V>) -> R): Map<R, V>
6. fun <K, V, R> Map<out K, V>.mapKeys(transform: (Map.Entry<K, V>) -> R): Map<R, V>
7. fun <K, V, R> Map<out K, V>.mapValues(transform: (Map.Entry<K, V>) -> R): Map<K, R>
8. fun <K, V, R, M : MutableMap<in K, in R>> Map<out K, V>.mapValuesTo(destination: M, transform: (Map.Entry<K, V>) -> R): M 

0. 실습을 위한 초기 데이터

data class Address(
    val street: String,
    val postcode: String
)
 
data class Customer(
    val firstName: String,
    val lastName: String,
    val age: Int
)

data class Person(
    val fullname: String,
    val age: Int,
    val address: Address
)

val customerMap = mapOf(Pair(Customer("Jack", "Davis", 25), Address("NANTERRE CT", "77471")),
                        Pair(Customer("Mary", "Taylor", 37), Address("W NORMA ST", "77009")),
                        Pair(Customer("Peter", "Thomas",17), Address("S NUGENT AVE", "77571")),
                        Pair(Customer("Amos", "Nelson",23), Address("E NAVAHO TRL", "77449")),
                        Pair(Customer("Craig", "White",45), Address("AVE N", "77587")),
                        Pair(Customer("Laura", "Lewis", 32), Address("NANTERRE CT", "77471")),
                        Pair(Customer("Steven", "Harris", 39), Address("S NUGENT AVE", "77571")),
                        Pair(Customer("Paul", "Moore", 18), Address("E NAVAHO TRL", "77449")),
                        Pair(Customer("Mary", "Cook", 61), Address("S NUGENT AVE", "77571")),
                        Pair(null, null))

1. 주어진 Kotlin 지도를 목록으로 변환

1.1 지도()