Merge pull request #1 from brianwernick/enum_converter_nullability

Updated the `EnumValueConverter` to be nullable & added tests

library/src/main/kotlin/com/devbrackets/android/datastore/converter/core/EnumValueConverter.kt

@@ -8,24 +8,27 @@ import kotlin.reflect.KClass
  * [Enum] in preferences. The [String] value represents
  * the `name` of the [Enum]
  */
-class EnumValueConverter<T: Enum<T>>(
-  private val enumClass: KClass<T>,
-  private val errorHandler: ErrorHandler<T> = DefaultErrorHandler()
-): ValueConverter<T, String> {
-  override fun toConverted(originalValue: T): String {
-    return originalValue.name
+class EnumValueConverter<E: Enum<E>, T: E?>(
+  private val enumClass: KClass<E>,
+  private val errorHandler: ErrorHandler<E, T> = DefaultErrorHandler<E,T>()
+): ValueConverter<T, String?> {
+  override fun toConverted(originalValue: T): String? {
+    return originalValue?.name
   }
 
-  override fun toOriginal(convertedValue: String): T {
-    return enumClass.java.enumConstants?.first {
-      it.name.equals(convertedValue, true)
-    } ?: errorHandler.onUnknownName(convertedValue, enumClass)
+  @Suppress("UNCHECKED_CAST")
+  override fun toOriginal(convertedValue: String?): T {
+    return convertedValue?.let { name ->
+      enumClass.java.enumConstants?.firstOrNull {
+        it.name.equals(name, true)
+      } ?: errorHandler.onUnknownName(convertedValue, enumClass)
+    } as T
   }
 
   /**
    * Defines how [EnumValueConverter] errors should be handled.
    */
-  fun interface ErrorHandler<T: Enum<T>> {
+  fun interface ErrorHandler<E: Enum<E>, T:E?> {
     /**
      * Called when a name (stored value) doesn't map to a defined Enum value for [enumClass].
      * This can happen if the name of a value is changed after it was stored.
@@ -34,15 +37,15 @@ class EnumValueConverter<T: Enum<T>>(
      * @param enumClass the [KClass] representing the destination Enum
      * @return The Enum value to use for the given [name]
      */
-    fun onUnknownName(name: String, enumClass: KClass<T>): T
+    fun onUnknownName(name: String?, enumClass: KClass<E>): T
   }
 
   /**
    * An implementation of [ErrorHandler] that throws an [IllegalArgumentException] when
    * any error occurs.
    */
-  class DefaultErrorHandler<T: Enum<T>>: ErrorHandler<T> {
-    override fun onUnknownName(name: String, enumClass: KClass<T>): T {
+  class DefaultErrorHandler<E: Enum<E>, T: E?>: ErrorHandler<E, T> {
+    override fun onUnknownName(name: String?, enumClass: KClass<E>): T {
       throw IllegalArgumentException("No Enum value of \"$name\" can be found for ${enumClass.simpleName}")
     }
   }

library/src/test/kotlin/com/devbrackets/android/datastore/converter/core/EnumValueConverterTest.kt

@@ -0,0 +1,72 @@
+package com.devbrackets.android.datastore.converter.core
+
+import org.junit.Assert
+import org.junit.Test
+
+class EnumValueConverterTest {
+
+  @Test
+  fun toConvertedNull() {
+    // Given
+    val converter = EnumValueConverter(TestEnum::class)
+
+    // When
+    val actual = converter.toConverted(null)
+
+    // Then
+    Assert.assertNull(actual)
+  }
+
+  @Test
+  fun toConvertedExists() {
+    // Given
+    val converter = EnumValueConverter(TestEnum::class)
+
+    // When
+    val actual = converter.toConverted(TestEnum.FIRST)
+
+    // Then
+    Assert.assertEquals("FIRST", actual)
+  }
+
+  @Test
+  fun toOriginalNull() {
+    // Given
+    val converter = EnumValueConverter(TestEnum::class)
+
+    // When
+    val actual = converter.toOriginal(null)
+
+    // Then
+    Assert.assertNull(actual)
+  }
+
+  @Test
+  fun toOriginalExists() {
+    // Given
+    val converter = EnumValueConverter(TestEnum::class)
+
+    // When
+    val actual = converter.toOriginal(TestEnum.SECOND.name)
+
+    // Then
+    Assert.assertEquals(TestEnum.SECOND, actual)
+  }
+
+  @Test
+  fun toOriginalNotExists() {
+    // Given
+    val converter = EnumValueConverter(TestEnum::class)
+
+    // When / Then
+    Assert.assertThrows(IllegalArgumentException::class.java) {
+      converter.toOriginal("FOURTH")
+    }
+  }
+
+  private enum class TestEnum {
+    FIRST,
+    SECOND,
+    THIRD
+  }
+}

libraryInfo.properties

@@ -1,7 +1,7 @@
 ARTIFACT_ID = datastore
 GROUP_ID = com.devbrackets.android
 
-VERSION_MAJOR = 0
+VERSION_MAJOR = 1
 VERSION_MINOR = 0
-VERSION_PATCH = 1
-VERSION_PRE_RELEASE = preview01
+VERSION_PATCH = 0
+VERSION_PRE_RELEASE = preview01