Kotlin reified

ReifiedSampleKotlinTest.kt

package ru.maksim.sample

import org.junit.jupiter.api.Test

class ReifiedSampleKotlinTest {

    @Test
    fun foo() {
        val shapeManager = ShapeManager()
        val circle = Circle(10.0)
        val circle2 = Circle(20.0)
        val rectangle = Rectangle(10.0, 20.0)
        val rectangle2 = Rectangle(20.0, 30.0)

        shapeManager.add(circle)
        shapeManager.add(circle2)
        shapeManager.add(rectangle)
        shapeManager.add(rectangle2)

        val circleFromList = ShapeManager.findByTypeWithoutReified(shapeManager.readOnlyShapes, Circle::class.java)
        println(circleFromList?.area())
        val circleFromList2 = ShapeManager.findByType<Circle>(shapeManager.readOnlyShapes)
        println(circleFromList2?.area())

        val circleFromList3 = ShapeManager.findByType<String>(shapeManager.readOnlyShapes)
        println(circleFromList3)
    }

}

interface Shape {
    fun area(): Double
}

class Rectangle(val width: Double, val height: Double) : Shape {
    override fun area() = width * height
}

class Circle(val radius: Double) : Shape {
    override fun area() = Math.PI * radius * radius
}

class ShapeManager {

    private val shapes = mutableListOf<Shape>()
    val readOnlyShapes: List<Shape> = shapes

    fun add(shape: Shape) {
        shapes.add(shape)
    }

    companion object {

        fun <T> findByTypeWithoutReified(shapes: List<Shape>, clazz: Class<T>): T? {
            shapes.forEach { shape ->
                if (clazz.isInstance(shape)) {
                    @Suppress("UNCHECKED_CAST")
                    return shape as T
                }
            }
            return null
        }

        inline fun <reified T> findByType(shapes: List<Shape>): T? {
            return shapes.find { it is T } as T?
        }
    }
}