Add an example custom adapter which delegates

examples/src/main/java/com/squareup/moshi/recipes/CustomAdapterWithDelegate.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2015 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi.recipes;
+
+
+import com.squareup.moshi.FromJson;
+import com.squareup.moshi.Json;
+import com.squareup.moshi.JsonAdapter;
+import com.squareup.moshi.Moshi;
+import com.squareup.moshi.JsonReader;
+
+import javax.annotation.Nullable;
+import java.io.IOException;
+
+public final class CustomAdapterWithDelegate {
+  public void run() throws Exception {
+    // We want to match any Stage that starts with 'in-progress' as Stage.IN_PROGRESS
+    // and leave the rest of the enum values as to match as normal.
+    Moshi moshi = new Moshi.Builder().add(new StageAdapter()).build();
+    JsonAdapter<Stage> jsonAdapter = moshi.adapter(Stage.class);
+
+    System.out.println(jsonAdapter.fromJson("\"not-started\""));
+    System.out.println(jsonAdapter.fromJson("\"in-progress\""));
+    System.out.println(jsonAdapter.fromJson("\"in-progress-step1\""));
+  }
+
+  public static void main(String[] args) throws Exception {
+    new CustomAdapterWithDelegate().run();
+  }
+
+  private enum Stage {
+    @Json(name = "not-started") NOT_STARTED,
+    @Json(name = "in-progress") IN_PROGRESS,
+    @Json(name = "rejected") REJECTED,
+    @Json(name = "completed") COMPLETED
+  }
+
+  private static final class StageAdapter {
+    @FromJson
+    @Nullable
+    Stage fromJson(JsonReader jsonReader, JsonAdapter<Stage> delegate) throws IOException {
+      String value = jsonReader.nextString();
+
+      Stage stage;
+      if (value.startsWith("in-progress")) {
+        stage = Stage.IN_PROGRESS;
+      } else {
+        stage = delegate.fromJsonValue(value);
+      }
+      return stage;
+    }
+  }
+}