리플렉션 기초

리플렉션이란 무엇인가요

KClass 가져오기

class Robot

fun main() {
    val fromType = Robot::class
    val fromInstance = Robot()::class
    println(fromType.simpleName)
    println(fromInstance.simpleName)
}

클래스의 이름

class Engine

fun main() {
    val k = Engine::class
    println(k.simpleName)
    println(k.qualifiedName)
}

속성 검사하기

import kotlin.reflect.full.memberProperties

class Point(val x: Int, val y: Int)

fun main() {
    for (p in Point::class.memberProperties) {
        println(p.name)
    }
}

속성 값 읽기

import kotlin.reflect.full.memberProperties

class Point(val x: Int, val y: Int)

fun main() {
    val p = Point(3, 4)
    for (prop in Point::class.memberProperties) {
        println(prop.name + " = " + prop.get(p))
    }
}

함수 검사하기

import kotlin.reflect.full.memberFunctions

class Calculator {
    fun add(a: Int, b: Int) = a + b
    fun negate(a: Int) = -a
}

fun main() {
    Calculator::class.memberFunctions
        .filter { it.name in listOf("add", "negate") }
        .forEach { println(it.name) }
}

함수 참조

fun double(n: Int) = n * 2

fun main() {
    val ref = ::double
    println(ref.name)
    println(ref.invoke(21))
}

인스턴스 만들기

import kotlin.reflect.full.createInstance

class Widget {
    override fun toString() = "Widget"
}

fun main() {
    val w = Widget::class.createInstance()
    println(w)
}

생성자 검사하기

class Person(val name: String, val age: Int)

fun main() {
    val ctor = Person::class.constructors.first()
    ctor.parameters.forEach { println(it.name) }
}

비용과 주의할 점

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