Iterate through object components

Author: thebaubau

kotlin-reflection/src/main/kotlin/com/baeldung/iterate/components/Circle.java

@@ -1,2 +1,9 @@
-package com.baeldung.iterate.components;public class Circle {
+package com.baeldung.iterate.components;
+
+public class Circle {
+    public static final double PI = 3.14;
+
+    public static double calculateArea(double radius) {
+        return PI * radius * radius;
+    }
 }

kotlin-reflection/src/main/kotlin/com/baeldung/iterate/components/Employee.kt

@@ -1,4 +1,16 @@
 package com.baeldung.iterate.components
 
-class Employee {
+open class Employee() {
+    var employeeId: Int = 0
+    var salary: Double = 0.0
+
+    val currentSalary: Double
+        get() = salary
+
+    val Employee.isSenior: Boolean
+        get() = salary >= 1000.0
+
+    fun Employee.isPromoted(): Boolean {
+        return salary >= 2000.0
+    }
 }

kotlin-reflection/src/main/kotlin/com/baeldung/iterate/components/Person.kt

@@ -1,4 +1,33 @@
 package com.baeldung.iterate.components
 
-class Person {
-}
+data class Person(val name: String, val age: Int) : Employee() {
+    val isAdult: Boolean
+        get() = age >= 18
+
+    val Person.isTeenager: Boolean
+        get() = age in 13..19
+
+    fun Person.isRetired(): Boolean {
+        return age >= 65
+    }
+
+    companion object Create {
+        fun create(name: String, age: Int) = Person(name, age)
+    }
+
+    data class Job(val title: String, val salary: Float)
+
+    object Address {
+        const val planet: String = "Earth"
+    }
+}
+
+fun Person.components(): Iterator<Pair<String, Any>> {
+    return listOf(
+        "name" to name,
+        "age" to age,
+        "isAdult" to isAdult,
+        "isTeenager" to isTeenager,
+        "isRetired" to isRetired()
+    ).iterator()
+}

kotlin-reflection/src/test/kotlin/com/baeldung/iterate/components/ReflectionInnerObjectsTests.kt

@@ -1,4 +1,25 @@
 package com.baeldung.iterate.components
 
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
 class ReflectionInnerObjectsTests {
+    @Test
+    fun `Get inner data class for Person`() {
+        val person = Person("Daniel", 37)
+
+        assertThat(person::class.nestedClasses)
+            .extracting("simpleName")
+            .contains("Job", "Address")
+    }
+
+    @Test
+    fun `Use iterator operator from Person`() {
+        val person = Person("Daniel", 37)
+        val properties = person.components().asSequence().toList()
+
+        assertThat(properties)
+            .extracting("first")
+            .containsOnly("name", "age", "isAdult", "isTeenager", "isRetired")
+    }
 }

kotlin-reflection/src/test/kotlin/com/baeldung/iterate/components/ReflectionIterationTests.kt

@@ -1,4 +1,108 @@
 package com.baeldung.iterate.components
 
-class ReflectionIteration {
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import kotlin.reflect.full.*
+
+class ReflectionIterationTests {
+    @Test
+    fun `Get data class members for Person`() {
+        val person = Person("Daniel", 37)
+
+        person::class.members.forEach {
+            println(it.name)
+        }
+
+        assertThat(person::class.members)
+            .extracting("name")
+            .contains("age", "name", "isAdult", "currentSalary", "employeeId", "salary")
+
+        person::class.declaredMembers.forEach {
+            println(it.name)
+        }
+
+        assertThat(person::class.declaredMembers)
+            .extracting("name")
+            .contains("age", "isAdult", "name")
+    }
+
+    @Test
+    fun `Get data class member properties for Person`() {
+        val person = Person("Daniel", 25)
+
+        assertThat(person::class.memberProperties)
+            .extracting("name")
+            .contains("age", "isAdult", "name", "employeeId", "salary")
+
+        assertThat(person::class.memberExtensionProperties)
+            .extracting("name")
+            .containsOnly("isTeenager", "isSenior")
+    }
+
+    @Test
+    fun `Get data class declared member properties for Person`() {
+        val person = Person("Daniel", 37)
+
+        assertThat(person::class.declaredMemberProperties)
+            .extracting("name")
+            .containsOnly("age", "isAdult", "name")
+
+        assertThat(person::class.declaredMemberExtensionProperties)
+            .extracting("name")
+            .containsOnly("isTeenager")
+    }
+
+    @Test
+    fun `Get Java class static properties`() {
+        val circle = Circle()
+
+        assertThat(Circle::class.staticProperties)
+            .extracting("name")
+            .containsOnly("PI")
+    }
+
+    @Test
+    fun `Get data class member functions for Person`() {
+        val person = Person("Daniel", 37)
+
+        assertThat(person::class.memberFunctions)
+            .extracting("name")
+            .contains("component1", "component2", "copy", "equals", "hashCode", "toString")
+
+        assertThat(person::class.memberExtensionFunctions)
+            .extracting("name")
+            .containsOnly("isRetired", "isPromoted")
+    }
+
+    @Test
+    fun `Get data class declared member functions for Person`() {
+        val person = Person("Daniel", 25)
+
+        assertThat(person::class.declaredMemberFunctions)
+            .extracting("name")
+            .contains("component1", "component2", "copy", "equals", "hashCode", "toString")
+
+        assertThat(person::class.declaredMemberExtensionFunctions)
+            .extracting("name")
+            .containsOnly("isRetired")
+    }
+
+    @Test
+    fun `Get data class static functions for Person`() {
+        val circle = Circle()
+
+        assertThat(circle::class.staticFunctions)
+            .extracting("name")
+            .contains("calculateArea")
+    }
+
+    @Test
+    fun `Get data class companion object for Person`() {
+        val person = Person("Daniel", 37)
+
+        assertThat(person::class.companionObject)
+            .isNotNull
+            .extracting("simpleName")
+            .isEqualTo("Create")
+    }
 }