Implemented JsonVariant comparisons with template friends

src/ArduinoJson/JsonVariantCasts.hpp

@@ -0,0 +1,60 @@
+// Copyright Benoit Blanchon 2014-2017
+// MIT License
+//
+// Arduino JSON library
+// https://bblanchon.github.io/ArduinoJson/
+// If you like this project, please add a star!
+
+#pragma once
+
+#include "Data/JsonVariantAs.hpp"
+#include "Polyfills/attributes.hpp"
+
+namespace ArduinoJson {
+
+template <typename TImpl>
+class JsonVariantCasts {
+ public:
+#if ARDUINOJSON_ENABLE_DEPRECATED
+  DEPRECATED("use as<JsonArray>() instead")
+  FORCE_INLINE JsonArray &asArray() const {
+    return impl()->template as<JsonArray>();
+  }
+
+  DEPRECATED("use as<JsonObject>() instead")
+  FORCE_INLINE JsonObject &asObject() const {
+    return impl()->template as<JsonObject>();
+  }
+
+  DEPRECATED("use as<char*>() instead")
+  FORCE_INLINE const char *asString() const {
+    return impl()->template as<const char *>();
+  }
+#endif
+
+  // Gets the variant as an array.
+  // Returns a reference to the JsonArray or JsonArray::invalid() if the
+  // variant
+  // is not an array.
+  FORCE_INLINE operator JsonArray &() const {
+    return impl()->template as<JsonArray &>();
+  }
+
+  // Gets the variant as an object.
+  // Returns a reference to the JsonObject or JsonObject::invalid() if the
+  // variant is not an object.
+  FORCE_INLINE operator JsonObject &() const {
+    return impl()->template as<JsonObject &>();
+  }
+
+  template <typename T>
+  FORCE_INLINE operator T() const {
+    return impl()->template as<T>();
+  }
+
+ private:
+  const TImpl *impl() const {
+    return static_cast<const TImpl *>(this);
+  }
+};
+}