Add enum extensions for serialization/deserialization

Author: enginebai

base/src/main/java/com/enginebai/base/extensions/EnumExt.kt

@@ -0,0 +1,89 @@
+package com.enginebai.base.extensions
+
+import com.google.gson.*
+import com.google.gson.annotations.SerializedName
+import retrofit2.Converter
+import retrofit2.Retrofit
+import timber.log.Timber
+import java.lang.reflect.Type
+
+/**
+ * Enable to serialize enum with Gson @SerializedName annotation to Retrofit HTTP query string.
+ *
+ * Example:
+ *  enum class MediaType {
+ *      @SerializedName("image-jpeg")
+ *      IMAGE_JPG,
+ *      @SerializedName("video-mp4")
+ *      VIDEO_MP4
+ *  }
+ *
+ *  interface ApiService {
+ *      @GET
+ *      fun getMediaList(@Query("type") mediaType: MediaType): List<Media>
+ *  }
+ *
+ *  val mediaList = apiService.getMediaList(MediaType.IMAGE_JPG)
+ *
+ * The actual HTTP request will be GET /medias?type=image-jpeg
+ */
+object EnumGsonSerializedNameConverterFactory : Converter.Factory() {
+    override fun stringConverter(
+        type: Type,
+        annotations: Array<out Annotation>,
+        retrofit: Retrofit
+    ): Converter<*, String>? {
+        if (type is Class<*> && type.isEnum) {
+            return Converter<Any?, String> { value -> getSerializedNameValue(value as Enum<*>) }
+        }
+        return null
+    }
+
+    private fun <E : Enum<*>> getSerializedNameValue(e: E): String {
+        val exception = IllegalStateException(
+            "You might miss the Gson @SerializedName annotation for " +
+                    "your enum class $e that is used for Retrofit request/response"
+        )
+        return e.javaClass.getField(e.name).getAnnotation(SerializedName::class.java)?.value
+            ?: throw exception
+    }
+}
+
+object EnumHasValueConverterFactory: Converter.Factory() {
+    override fun stringConverter(
+        type: Type,
+        annotations: Array<out Annotation>,
+        retrofit: Retrofit
+    ): Converter<*, String>? {
+        if (type is Class<*> && type.isEnum && type.interfaces.contains(EnumHasValue::class.java)) {
+            return Converter<Any?, String> { value -> (value as EnumHasValue).value }
+        }
+        return null
+    }
+}
+
+// source: https://stackoverflow.com/a/45561053/2279285
+interface EnumHasValue {
+    val value: String
+}
+
+class EnumHasValueJsonAdapter<T> : JsonSerializer<T>, JsonDeserializer<T> where T : EnumHasValue {
+    override fun serialize(
+        src: T,
+        typeOfSrc: Type?,
+        context: JsonSerializationContext?
+    ): JsonElement {
+        return JsonPrimitive(src.value)
+    }
+
+    override fun deserialize(
+        json: JsonElement,
+        typeOfT: Type?,
+        context: JsonDeserializationContext?
+    ): T? {
+        val parsedValue = (typeOfT as Class<T>).enumConstants?.associateBy { it.value }?.get(json.asString)
+        parsedValue ?: kotlin.run { Timber.w("Can not deserialize value ${json.asString} to $typeOfT") }
+        return parsedValue
+    }
+
+}

base/src/main/java/com/enginebai/base/view/BaseActivity.kt

@@ -5,6 +5,7 @@ import androidx.annotation.LayoutRes
 import androidx.appcompat.app.AppCompatActivity
 import io.reactivex.disposables.CompositeDisposable
 import io.reactivex.disposables.Disposable
+import timber.log.Timber
 
 abstract class BaseActivity : AppCompatActivity() {
 
@@ -13,8 +14,6 @@ abstract class BaseActivity : AppCompatActivity() {
     @LayoutRes
     abstract fun getLayoutId(): Int
 
-    abstract fun handleErrorMessage(message: String)
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(getLayoutId())
@@ -25,6 +24,10 @@ abstract class BaseActivity : AppCompatActivity() {
         super.onDestroy()
     }
 
+    open fun handleErrorMessage(message: String) {
+        Timber.w(message)
+    }
+
     protected fun Disposable.disposeOnDestroy(): Disposable {
         disposables.add(this)
         return disposables