diff --git a/CHANGELOG.md b/CHANGELOG.md
index 657388601..2a7a2f4fc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,10 @@
 ArduinoJson: change log
 =======================
 
-v5.0 (currently in development)
+v5.0 (currently under development)
 ----
 
+* Added support of `String` class (issue #55, #56, #70, #77)
 * Redesigned `JsonVariant` to leverage converting constructors instead of assignment operators.
 
 **BREAKING CHANGES**:
@@ -11,6 +12,13 @@ v5.0 (currently in development)
 - `JsonArray::at()` and `JsonObject::at()` were renamed to `get()`
 - Number of digits of floating point value are now set with `double_with_n_digits()`
 
+**Personal note about the `String` class**:
+Support of the `String` class has been added to the library because many people use it in their programs.
+However, you should not see this as an invitation to use the `String` class.
+The `String` class is **bad** because it uses dynamic memory allocation.
+Compared to static allocation, it compiles to a bigger, slower program, and is less predicate.
+You certainly don't want that in an embedded environment!
+
 v4.4
 ----
 
@@ -143,4 +151,4 @@ v1.1
 v1.0 
 ----
 
-Initial release
\ No newline at end of file
+Initial release
diff --git a/include/ArduinoJson/Arduino/String.hpp b/include/ArduinoJson/Arduino/String.hpp
new file mode 100644
index 000000000..3ddf246de
--- /dev/null
+++ b/include/ArduinoJson/Arduino/String.hpp
@@ -0,0 +1,19 @@
+// Copyright Benoit Blanchon 2014-2015
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+
+#pragma once
+
+#ifndef ARDUINO
+
+#include <string>
+
+typedef std::string String;
+
+#else
+
+#include <WString.h>
+
+#endif
diff --git a/include/ArduinoJson/Internals/ForceInline.hpp b/include/ArduinoJson/Internals/ForceInline.hpp
index fd43e7a7b..322e30b31 100644
--- a/include/ArduinoJson/Internals/ForceInline.hpp
+++ b/include/ArduinoJson/Internals/ForceInline.hpp
@@ -7,7 +7,7 @@
 #pragma once
 
 #ifdef _MSC_VER
-#define JSON_FORCE_INLINE __forceinline
+#define FORCE_INLINE __forceinline
 #else
-#define JSON_FORCE_INLINE __attribute__((always_inline))
+#define FORCE_INLINE __attribute__((always_inline))
 #endif
diff --git a/include/ArduinoJson/Internals/JsonParser.hpp b/include/ArduinoJson/Internals/JsonParser.hpp
index c244ca8e8..9d8278a1d 100644
--- a/include/ArduinoJson/Internals/JsonParser.hpp
+++ b/include/ArduinoJson/Internals/JsonParser.hpp
@@ -29,7 +29,7 @@ class JsonParser {
   void skipSpaces();
 
   bool parseAnythingTo(JsonVariant *destination);
-  JSON_FORCE_INLINE bool parseAnythingToUnsafe(JsonVariant *destination);
+  FORCE_INLINE bool parseAnythingToUnsafe(JsonVariant *destination);
 
   const char *parseString();
 
diff --git a/include/ArduinoJson/Internals/JsonVariantContent.ipp b/include/ArduinoJson/Internals/JsonVariantContent.ipp
index 2c5a9ae68..c5fb36c0a 100644
--- a/include/ArduinoJson/Internals/JsonVariantContent.ipp
+++ b/include/ArduinoJson/Internals/JsonVariantContent.ipp
@@ -23,6 +23,11 @@ inline char const* JsonVariantContent::as<char const*>() const {
   return asString;
 }
 
+template <>
+inline String JsonVariantContent::as<String>() const {
+  return asString;
+}
+
 template <>
 inline double JsonVariantContent::as<double>() const {
   return asDouble;
diff --git a/include/ArduinoJson/Internals/List.hpp b/include/ArduinoJson/Internals/List.hpp
index 675ed3b21..d5dc5976f 100644
--- a/include/ArduinoJson/Internals/List.hpp
+++ b/include/ArduinoJson/Internals/List.hpp
@@ -48,22 +48,7 @@ class List {
   const_iterator end() const { return const_iterator(NULL); }
 
  protected:
-  node_type *addNewNode() {
-    if (!_buffer) return NULL;
-
-    node_type *newNode = new (_buffer) node_type();
-
-    if (_firstNode) {
-      node_type *lastNode = _firstNode;
-      while (lastNode->next) lastNode = lastNode->next;
-      lastNode->next = newNode;
-    } else {
-      _firstNode = newNode;
-    }
-
-    return newNode;
-  }
-
+  node_type *addNewNode();
   void removeNode(node_type *nodeToRemove);
 
   JsonBuffer *_buffer;
diff --git a/include/ArduinoJson/JsonArray.hpp b/include/ArduinoJson/JsonArray.hpp
index 78e580697..3c8c3a7e5 100644
--- a/include/ArduinoJson/JsonArray.hpp
+++ b/include/ArduinoJson/JsonArray.hpp
@@ -42,27 +42,27 @@ class JsonArray : public Internals::JsonPrintable<JsonArray>,
       : Internals::List<JsonVariant>(buffer) {}
 
   // Gets the value at the specified index
-  JSON_FORCE_INLINE const JsonArraySubscript operator[](size_t index) const;
+  FORCE_INLINE const JsonArraySubscript operator[](size_t index) const;
 
   // Gets or sets the value at specified index
-  JSON_FORCE_INLINE JsonArraySubscript operator[](size_t index);
+  FORCE_INLINE JsonArraySubscript operator[](size_t index);
 
   // Adds the specified value at the end of the array.
-  JSON_FORCE_INLINE bool add(const JsonVariant value);
+  FORCE_INLINE bool add(const JsonVariant value);
 
   // Sets the value at specified index.
-  JSON_FORCE_INLINE void set(size_t index, const JsonVariant value);
+  FORCE_INLINE void set(size_t index, const JsonVariant value);
 
   // Gets the value at the specified index.
-  JSON_FORCE_INLINE JsonVariant get(size_t index) const;
+  FORCE_INLINE JsonVariant get(size_t index) const;
 
   // Gets the value at the specified index.
   template <typename T>
-  JSON_FORCE_INLINE T get(size_t index) const;
+  FORCE_INLINE T get(size_t index) const;
 
   // Check the type of the value at specified index.
   template <typename T>
-  JSON_FORCE_INLINE T is(size_t index) const;
+  FORCE_INLINE T is(size_t index) const;
 
   // Creates a JsonArray and adds a reference at the end of the array.
   // It's a shortcut for JsonBuffer::createArray() and JsonArray::add()
diff --git a/include/ArduinoJson/JsonArraySubscript.hpp b/include/ArduinoJson/JsonArraySubscript.hpp
index 52ba828fd..4f2aca38c 100644
--- a/include/ArduinoJson/JsonArraySubscript.hpp
+++ b/include/ArduinoJson/JsonArraySubscript.hpp
@@ -11,25 +11,32 @@
 namespace ArduinoJson {
 class JsonArraySubscript : public JsonVariantBase<JsonArraySubscript> {
  public:
-  JSON_FORCE_INLINE JsonArraySubscript(JsonArray& array, size_t index)
+  FORCE_INLINE JsonArraySubscript(JsonArray& array, size_t index)
       : _array(array), _index(index) {}
 
-  JSON_FORCE_INLINE JsonArraySubscript& operator=(const JsonVariant& value) {
+  FORCE_INLINE JsonArraySubscript& operator=(const JsonVariant& value) {
     _array.set(_index, value);
     return *this;
   }
 
-  JSON_FORCE_INLINE bool success() const { return _index < _array.size(); }
+  FORCE_INLINE JsonArraySubscript& operator=(const JsonArraySubscript& other) {
+    // to prevent Visual Studio warning C4512: assignment operator could not be
+    // generated
+    _array.set(_index, other._array.get(other._index));
+    return *this;
+  }
+
+  FORCE_INLINE bool success() const { return _index < _array.size(); }
 
-  JSON_FORCE_INLINE operator JsonVariant() const { return _array.get(_index); }
+  FORCE_INLINE operator JsonVariant() const { return _array.get(_index); }
 
   template <typename T>
-  JSON_FORCE_INLINE T as() const {
+  FORCE_INLINE T as() const {
     return _array.get<T>(_index);
   }
 
   template <typename T>
-  JSON_FORCE_INLINE T is() const {
+  FORCE_INLINE T is() const {
     return _array.is<T>(_index);
   }
 
diff --git a/include/ArduinoJson/JsonBuffer.hpp b/include/ArduinoJson/JsonBuffer.hpp
index aab79800f..e1ef3b818 100644
--- a/include/ArduinoJson/JsonBuffer.hpp
+++ b/include/ArduinoJson/JsonBuffer.hpp
@@ -9,6 +9,8 @@
 #include <stddef.h>  // for size_t
 #include <stdint.h>  // for uint8_t
 
+#include "Arduino/String.hpp"
+
 #if defined(__clang__)
 #pragma clang diagnostic ignored "-Wnon-virtual-dtor"
 #elif defined(__GNUC__)
@@ -55,6 +57,11 @@ class JsonBuffer {
   // allocation fails.
   JsonArray &parseArray(char *json, uint8_t nestingLimit = DEFAULT_LIMIT);
 
+  // Same as above with a String class
+  JsonArray &parseArray(const String &json, uint8_t nesting = DEFAULT_LIMIT) {
+    return parseArray(const_cast<char *>(json.c_str()), nesting);
+  }
+
   // Allocates and populate a JsonObject from a JSON string.
   //
   // The First argument is a pointer to the JSON string, the memory must be
@@ -67,6 +74,12 @@ class JsonBuffer {
   // allocation fails.
   JsonObject &parseObject(char *json, uint8_t nestingLimit = DEFAULT_LIMIT);
 
+  // Same as above with a String class
+  JsonObject &parseObject(const String &json,
+                          uint8_t nestingLimit = DEFAULT_LIMIT) {
+    return parseObject(const_cast<char *>(json.c_str()), nestingLimit);
+  }
+
   // Allocates n bytes in the JsonBuffer.
   // Return a pointer to the allocated memory or NULL if allocation fails.
   virtual void *alloc(size_t size) = 0;
diff --git a/include/ArduinoJson/JsonObject.hpp b/include/ArduinoJson/JsonObject.hpp
index 48d1ae185..d5da8e9e1 100644
--- a/include/ArduinoJson/JsonObject.hpp
+++ b/include/ArduinoJson/JsonObject.hpp
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include "Arduino/String.hpp"
 #include "Internals/JsonBufferAllocated.hpp"
 #include "Internals/JsonPrintable.hpp"
 #include "Internals/List.hpp"
@@ -35,62 +36,59 @@ class JsonObject : public Internals::JsonPrintable<JsonObject>,
                    public Internals::List<JsonPair>,
                    public Internals::JsonBufferAllocated {
  public:
-  typedef const char *key_type;
-  typedef JsonPair value_type;
-
   // Create an empty JsonArray attached to the specified JsonBuffer.
   // You should not use this constructor directly.
   // Instead, use JsonBuffer::createObject() or JsonBuffer.parseObject().
-  JSON_FORCE_INLINE explicit JsonObject(JsonBuffer *buffer)
+  FORCE_INLINE explicit JsonObject(JsonBuffer* buffer)
       : Internals::List<JsonPair>(buffer) {}
 
   // Gets or sets the value associated with the specified key.
-  JSON_FORCE_INLINE JsonObjectSubscript operator[](key_type key);
+  FORCE_INLINE JsonObjectSubscript operator[](JsonObjectKey key);
 
   // Gets the value associated with the specified key.
-  JSON_FORCE_INLINE const JsonObjectSubscript operator[](key_type key) const;
+  FORCE_INLINE const JsonObjectSubscript operator[](JsonObjectKey key) const;
 
   // Sets the specified key with the specified value.
-  JSON_FORCE_INLINE bool set(key_type key, const JsonVariant value);
+  FORCE_INLINE bool set(JsonObjectKey key, JsonVariant value);
 
   // Gets the value associated with the specified key.
-  JSON_FORCE_INLINE JsonVariant get(key_type key) const;
+  FORCE_INLINE JsonVariant get(JsonObjectKey) const;
 
   // Gets the value associated with the specified key.
   template <typename T>
-  JSON_FORCE_INLINE T get(key_type key) const;
+  FORCE_INLINE T get(JsonObjectKey) const;
 
   // Checks the type of the value associated with the specified key.
   template <typename T>
-  JSON_FORCE_INLINE T is(key_type key) const;
+  FORCE_INLINE bool is(JsonObjectKey) const;
 
   // Creates and adds a JsonArray.
   // This is a shortcut for JsonBuffer::createArray() and JsonObject::add().
-  JsonArray &createNestedArray(key_type key);
+  JsonArray& createNestedArray(JsonObjectKey key);
 
   // Creates and adds a JsonObject.
   // This is a shortcut for JsonBuffer::createObject() and JsonObject::add().
-  JsonObject &createNestedObject(key_type key);
+  JsonObject& createNestedObject(JsonObjectKey key);
 
   // Tells weither the specified key is present and associated with a value.
-  JSON_FORCE_INLINE bool containsKey(key_type key) const;
+  FORCE_INLINE bool containsKey(JsonObjectKey key) const;
 
   // Removes the specified key and the associated value.
-  void remove(key_type key);
+  void remove(JsonObjectKey key);
 
   // Returns a reference an invalid JsonObject.
   // This object is meant to replace a NULL pointer.
   // This is used when memory allocation or JSON parsing fail.
-  static JsonObject &invalid() { return _invalid; }
+  static JsonObject& invalid() { return _invalid; }
 
   // Serialize the object to the specified JsonWriter
-  void writeTo(Internals::JsonWriter &writer) const;
+  void writeTo(Internals::JsonWriter& writer) const;
 
  private:
   // Returns the list node that matches the specified key.
-  node_type *getNodeAt(key_type key) const;
+  node_type* getNodeAt(JsonObjectKey key) const;
 
-  node_type *getOrCreateNodeAt(const char *key);
+  node_type* getOrCreateNodeAt(JsonObjectKey key);
 
   // The instance returned by JsonObject::invalid()
   static JsonObject _invalid;
diff --git a/include/ArduinoJson/JsonObject.ipp b/include/ArduinoJson/JsonObject.ipp
index a0e3a43b2..ab57dc514 100644
--- a/include/ArduinoJson/JsonObject.ipp
+++ b/include/ArduinoJson/JsonObject.ipp
@@ -11,38 +11,41 @@
 
 namespace ArduinoJson {
 
-inline JsonVariant JsonObject::get(key_type key) const {
+inline JsonVariant JsonObject::get(JsonObjectKey key) const {
   node_type *node = getNodeAt(key);
   return node ? node->content.value : JsonVariant();
 }
 
 template <typename T>
-inline T JsonObject::get(key_type key) const {
+inline T JsonObject::get(JsonObjectKey key) const {
   node_type *node = getNodeAt(key);
   return node ? node->content.value.as<T>() : JsonVariant::invalid<T>();
 }
 
 template <typename T>
-inline T JsonObject::is(key_type key) const {
+inline bool JsonObject::is(JsonObjectKey key) const {
   node_type *node = getNodeAt(key);
   return node ? node->content.value.is<T>() : false;
 }
 
-inline JsonObjectSubscript JsonObject::operator[](key_type key) {
+inline JsonObjectSubscript JsonObject::operator[](JsonObjectKey key) {
   return JsonObjectSubscript(*this, key);
 }
 
-inline const JsonObjectSubscript JsonObject::operator[](key_type key) const {
+inline const JsonObjectSubscript JsonObject::operator[](
+    JsonObjectKey key) const {
   return JsonObjectSubscript(*const_cast<JsonObject *>(this), key);
 }
 
-inline bool JsonObject::containsKey(key_type key) const {
+inline bool JsonObject::containsKey(JsonObjectKey key) const {
   return getNodeAt(key) != NULL;
 }
 
-inline void JsonObject::remove(key_type key) { removeNode(getNodeAt(key)); }
+inline void JsonObject::remove(JsonObjectKey key) {
+  removeNode(getNodeAt(key));
+}
 
-inline bool JsonObject::set(const char *key, const JsonVariant value) {
+inline bool JsonObject::set(JsonObjectKey key, const JsonVariant value) {
   node_type *node = getOrCreateNodeAt(key);
   if (!node) return false;
 
@@ -57,6 +60,12 @@ inline const JsonObjectSubscript JsonVariantBase<TImplem>::operator[](
   return asObject()[key];
 }
 
+template <typename TImplem>
+inline const JsonObjectSubscript JsonVariantBase<TImplem>::operator[](
+    const String &key) const {
+  return asObject()[key];
+}
+
 template <>
 inline JsonObject const &JsonVariant::invalid<JsonObject const &>() {
   return JsonObject::invalid();
diff --git a/include/ArduinoJson/JsonObjectKey.hpp b/include/ArduinoJson/JsonObjectKey.hpp
new file mode 100644
index 000000000..a9a398a56
--- /dev/null
+++ b/include/ArduinoJson/JsonObjectKey.hpp
@@ -0,0 +1,24 @@
+// Copyright Benoit Blanchon 2014-2015
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+
+#pragma once
+
+#include "Arduino/String.hpp"
+
+namespace ArduinoJson {
+
+class JsonObjectKey {
+ public:
+  JsonObjectKey() {}
+  JsonObjectKey(const char* key) : _data(key) {}
+  JsonObjectKey(const String& key) : _data(key.c_str()) {}
+
+  operator const char*() const { return _data; }
+
+ private:
+  const char* _data;
+};
+}
diff --git a/include/ArduinoJson/JsonObjectSubscript.hpp b/include/ArduinoJson/JsonObjectSubscript.hpp
index 70f4a2292..77034713b 100644
--- a/include/ArduinoJson/JsonObjectSubscript.hpp
+++ b/include/ArduinoJson/JsonObjectSubscript.hpp
@@ -11,30 +11,38 @@
 namespace ArduinoJson {
 class JsonObjectSubscript : public JsonVariantBase<JsonObjectSubscript> {
  public:
-  JSON_FORCE_INLINE JsonObjectSubscript(JsonObject& object, const char* key)
+  FORCE_INLINE JsonObjectSubscript(JsonObject& object, JsonObjectKey key)
       : _object(object), _key(key) {}
 
-  JSON_FORCE_INLINE JsonObjectSubscript& operator=(const JsonVariant& value) {
+  FORCE_INLINE JsonObjectSubscript& operator=(const JsonVariant& value) {
     _object.set(_key, value);
     return *this;
   }
 
-  JSON_FORCE_INLINE bool success() const { return _object.containsKey(_key); }
+  FORCE_INLINE JsonObjectSubscript& operator=(
+      const JsonObjectSubscript& other) {
+    // to prevent Visual Studio warning C4512: assignment operator could not be
+    // generated
+    _object.set(_key, other._object.get(other._key));
+    return *this;
+  }
+
+  FORCE_INLINE bool success() const { return _object.containsKey(_key); }
 
-  JSON_FORCE_INLINE operator JsonVariant() const { return _object.get(_key); }
+  FORCE_INLINE operator JsonVariant() const { return _object.get(_key); }
 
   template <typename T>
-  JSON_FORCE_INLINE T as() const {
+  FORCE_INLINE T as() const {
     return _object.get<T>(_key);
   }
 
   template <typename T>
-  JSON_FORCE_INLINE T is() const {
+  FORCE_INLINE T is() const {
     return _object.is<T>(_key);
   }
 
  private:
   JsonObject& _object;
-  const char* _key;
+  JsonObjectKey _key;
 };
 }
diff --git a/include/ArduinoJson/JsonPair.hpp b/include/ArduinoJson/JsonPair.hpp
index 876a66cc0..0b6122bea 100644
--- a/include/ArduinoJson/JsonPair.hpp
+++ b/include/ArduinoJson/JsonPair.hpp
@@ -6,13 +6,14 @@
 
 #pragma once
 
+#include "JsonObjectKey.hpp"
 #include "JsonVariant.hpp"
 
 namespace ArduinoJson {
 
 // A key value pair for JsonObject.
 struct JsonPair {
-  const char* key;
+  JsonObjectKey key;
   JsonVariant value;
 };
 }
diff --git a/include/ArduinoJson/JsonVariant.hpp b/include/ArduinoJson/JsonVariant.hpp
index a093264f1..0afd4b78c 100644
--- a/include/ArduinoJson/JsonVariant.hpp
+++ b/include/ArduinoJson/JsonVariant.hpp
@@ -9,6 +9,7 @@
 #include <stddef.h>
 #include <stdint.h>  // for uint8_t
 
+#include "Arduino/String.hpp"
 #include "Internals/JsonPrintable.hpp"
 #include "Internals/JsonVariantContent.hpp"
 #include "Internals/JsonVariantType.hpp"
@@ -31,46 +32,47 @@ class JsonVariant : public Internals::JsonPrintable<JsonVariant>,
                     public JsonVariantBase<JsonVariant> {
  public:
   // Creates an uninitialized JsonVariant
-  JSON_FORCE_INLINE JsonVariant() : _type(Internals::JSON_UNDEFINED) {}
+  FORCE_INLINE JsonVariant() : _type(Internals::JSON_UNDEFINED) {}
 
   // Create a JsonVariant containing a boolean value.
   // It will be serialized as "true" or "false" in JSON.
-  JSON_FORCE_INLINE JsonVariant(bool value);
+  FORCE_INLINE JsonVariant(bool value);
 
   // Create a JsonVariant containing a floating point value.
   // The second argument specifies the number of decimal digits to write in
   // the JSON string.
-  JSON_FORCE_INLINE JsonVariant(float value, uint8_t decimals = 2);
-  JSON_FORCE_INLINE JsonVariant(double value, uint8_t decimals = 2);
+  FORCE_INLINE JsonVariant(float value, uint8_t decimals = 2);
+  FORCE_INLINE JsonVariant(double value, uint8_t decimals = 2);
 
   // Create a JsonVariant containing an integer value.
-  JSON_FORCE_INLINE JsonVariant(signed char value);
-  JSON_FORCE_INLINE JsonVariant(signed long value);
-  JSON_FORCE_INLINE JsonVariant(signed int value);
-  JSON_FORCE_INLINE JsonVariant(signed short value);
-  JSON_FORCE_INLINE JsonVariant(unsigned char value);
-  JSON_FORCE_INLINE JsonVariant(unsigned long value);
-  JSON_FORCE_INLINE JsonVariant(unsigned int value);
-  JSON_FORCE_INLINE JsonVariant(unsigned short value);
+  FORCE_INLINE JsonVariant(signed char value);
+  FORCE_INLINE JsonVariant(signed long value);
+  FORCE_INLINE JsonVariant(signed int value);
+  FORCE_INLINE JsonVariant(signed short value);
+  FORCE_INLINE JsonVariant(unsigned char value);
+  FORCE_INLINE JsonVariant(unsigned long value);
+  FORCE_INLINE JsonVariant(unsigned int value);
+  FORCE_INLINE JsonVariant(unsigned short value);
 
   // Create a JsonVariant containing a string.
-  JSON_FORCE_INLINE JsonVariant(const char *value);
+  FORCE_INLINE JsonVariant(const char *value);
+  FORCE_INLINE JsonVariant(const String &value);
 
   // Create a JsonVariant containing a reference to an array.
-  JSON_FORCE_INLINE JsonVariant(JsonArray &array);
+  FORCE_INLINE JsonVariant(JsonArray &array);
 
   // Create a JsonVariant containing a reference to an object.
-  JSON_FORCE_INLINE JsonVariant(JsonObject &object);
+  FORCE_INLINE JsonVariant(JsonObject &object);
 
   // Get the variant as the specified type.
   // See cast operators for details.
   template <typename T>
-  JSON_FORCE_INLINE T as() const;
+  FORCE_INLINE T as() const;
 
   // Tells weither the variant has the specified type.
   // Returns true if the variant has type type T, false otherwise.
   template <typename T>
-  JSON_FORCE_INLINE bool is() const;
+  FORCE_INLINE bool is() const;
 
   // Serialize the variant to a JsonWriter
   void writeTo(Internals::JsonWriter &writer) const;
diff --git a/include/ArduinoJson/JsonVariant.ipp b/include/ArduinoJson/JsonVariant.ipp
index c41366275..35460572d 100644
--- a/include/ArduinoJson/JsonVariant.ipp
+++ b/include/ArduinoJson/JsonVariant.ipp
@@ -20,6 +20,11 @@ inline JsonVariant::JsonVariant(const char *value) {
   _content.asString = value;
 }
 
+inline JsonVariant::JsonVariant(const String &value) {
+  _type = Internals::JSON_STRING;
+  _content.asString = value.c_str();
+}
+
 inline JsonVariant::JsonVariant(double value, uint8_t decimals) {
   _type = static_cast<Internals::JsonVariantType>(
       Internals::JSON_DOUBLE_0_DECIMALS + decimals);
@@ -107,6 +112,11 @@ inline bool JsonVariant::is<char const *>() const {
   return _type == Internals::JSON_STRING;
 }
 
+template <>
+inline bool JsonVariant::is<String>() const {
+  return _type == Internals::JSON_STRING;
+}
+
 template <>
 inline bool JsonVariant::is<double>() const {
   return _type >= Internals::JSON_DOUBLE_0_DECIMALS;
diff --git a/include/ArduinoJson/JsonVariantBase.hpp b/include/ArduinoJson/JsonVariantBase.hpp
index c9a331ada..6939702f2 100644
--- a/include/ArduinoJson/JsonVariantBase.hpp
+++ b/include/ArduinoJson/JsonVariantBase.hpp
@@ -7,6 +7,7 @@
 #pragma once
 
 #include "Internals/ForceInline.hpp"
+#include "JsonObjectKey.hpp"
 
 namespace ArduinoJson {
 
@@ -19,50 +20,45 @@ class JsonVariantBase {
  public:
   // Gets the variant as a boolean value.
   // Returns false if the variant is not a boolean value.
-  JSON_FORCE_INLINE operator bool() const { return as<bool>(); }
+  FORCE_INLINE operator bool() const { return as<bool>(); }
 
   // Gets the variant as a floating-point value.
   // Returns 0.0 if the variant is not a floating-point value
-  JSON_FORCE_INLINE operator double() const { return as<double>(); }
-  JSON_FORCE_INLINE operator float() const { return as<float>(); }
+  FORCE_INLINE operator double() const { return as<double>(); }
+  FORCE_INLINE operator float() const { return as<float>(); }
 
   // Gets the variant as an integer value.
   // Returns 0 if the variant is not an integer value.
-  JSON_FORCE_INLINE operator signed long() const { return as<signed long>(); }
-  JSON_FORCE_INLINE operator signed char() const { return as<signed char>(); }
-  JSON_FORCE_INLINE operator signed int() const { return as<signed int>(); }
-  JSON_FORCE_INLINE operator signed short() const { return as<signed short>(); }
-  JSON_FORCE_INLINE operator unsigned char() const {
-    return as<unsigned char>();
-  }
-  JSON_FORCE_INLINE operator unsigned int() const { return as<unsigned int>(); }
-  JSON_FORCE_INLINE operator unsigned long() const {
-    return as<unsigned long>();
-  }
-  JSON_FORCE_INLINE operator unsigned short() const {
-    return as<unsigned short>();
-  }
+  FORCE_INLINE operator signed long() const { return as<signed long>(); }
+  FORCE_INLINE operator signed char() const { return as<signed char>(); }
+  FORCE_INLINE operator signed int() const { return as<signed int>(); }
+  FORCE_INLINE operator signed short() const { return as<signed short>(); }
+  FORCE_INLINE operator unsigned char() const { return as<unsigned char>(); }
+  FORCE_INLINE operator unsigned int() const { return as<unsigned int>(); }
+  FORCE_INLINE operator unsigned long() const { return as<unsigned long>(); }
+  FORCE_INLINE operator unsigned short() const { return as<unsigned short>(); }
 
   // Gets the variant as a string.
   // Returns NULL if variant is not a string.
-  JSON_FORCE_INLINE operator const char *() const { return as<const char *>(); }
-  JSON_FORCE_INLINE const char *asString() const { return as<const char *>(); }
+  FORCE_INLINE operator const char *() const { return as<const char *>(); }
+  FORCE_INLINE const char *asString() const { return as<const char *>(); }
+  FORCE_INLINE operator String() const { return as<String>(); }
 
   // Gets the variant as an array.
   // Returns a reference to the JsonArray or JsonArray::invalid() if the
   // variant
   // is not an array.
-  JSON_FORCE_INLINE operator JsonArray &() const { return as<JsonArray &>(); }
-  JSON_FORCE_INLINE JsonArray &asArray() const { return as<JsonArray &>(); }
+  FORCE_INLINE operator JsonArray &() const { return as<JsonArray &>(); }
+  FORCE_INLINE JsonArray &asArray() const { return as<JsonArray &>(); }
 
   // Gets the variant as an object.
   // Returns a reference to the JsonObject or JsonObject::invalid() if the
   // variant is not an object.
-  JSON_FORCE_INLINE operator JsonObject &() const { return as<JsonObject &>(); }
-  JSON_FORCE_INLINE JsonObject &asObject() const { return as<JsonObject &>(); }
+  FORCE_INLINE operator JsonObject &() const { return as<JsonObject &>(); }
+  FORCE_INLINE JsonObject &asObject() const { return as<JsonObject &>(); }
 
   template <typename T>
-  JSON_FORCE_INLINE const T as() const {
+  FORCE_INLINE const T as() const {
     return impl()->template as<T>();
   }
 
@@ -74,13 +70,17 @@ class JsonVariantBase {
   // Mimics an array.
   // Returns the element at specified index if the variant is an array.
   // Returns JsonVariant::invalid() if the variant is not an array.
-  JSON_FORCE_INLINE const JsonArraySubscript operator[](int index) const;
+  FORCE_INLINE const JsonArraySubscript operator[](int index) const;
 
   // Mimics an object.
   // Returns the value associated with the specified key if the variant is
   // an object.
   // Return JsonVariant::invalid() if the variant is not an object.
-  JSON_FORCE_INLINE const JsonObjectSubscript operator[](const char *key) const;
+  FORCE_INLINE const JsonObjectSubscript operator[](const char *key) const;
+  FORCE_INLINE const JsonObjectSubscript operator[](const String &key) const;
+
+ protected:
+  JsonVariantBase() {}
 
  private:
   const TImpl *impl() const { return static_cast<const TImpl *>(this); }
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 2fe98745a..2a383ea0a 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,5 +1,6 @@
-file(GLOB_RECURSE INC_FILES ../include/*.hpp)
-file(GLOB_RECURSE SRC_FILES *.cpp)
+file(GLOB_RECURSE HPP_FILES ../include/*.hpp)
+file(GLOB_RECURSE IPP_FILES ../include/*.ipp)
+file(GLOB_RECURSE CPP_FILES *.cpp)
 
 if(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang)")
 	add_definitions(
@@ -45,4 +46,4 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 	)
 endif()
 
-add_library(ArduinoJson ${SRC_FILES} ${INC_FILES})
\ No newline at end of file
+add_library(ArduinoJson ${CPP_FILES} ${HPP_FILES} ${IPP_FILES})
diff --git a/src/Internals/List.cpp b/src/Internals/List.cpp
index 00ed3efe9..96f8503a1 100644
--- a/src/Internals/List.cpp
+++ b/src/Internals/List.cpp
@@ -19,6 +19,23 @@ size_t List<T>::size() const {
   return nodeCount;
 }
 
+template <typename T>
+typename List<T>::node_type *List<T>::addNewNode() {
+  if (!_buffer) return NULL;
+
+  node_type *newNode = new (_buffer) node_type();
+
+  if (_firstNode) {
+    node_type *lastNode = _firstNode;
+    while (lastNode->next) lastNode = lastNode->next;
+    lastNode->next = newNode;
+  } else {
+    _firstNode = newNode;
+  }
+
+  return newNode;
+}
+
 template <typename T>
 void List<T>::removeNode(node_type *nodeToRemove) {
   if (!nodeToRemove) return;
diff --git a/src/JsonObject.cpp b/src/JsonObject.cpp
index 1cc29859a..77aae4137 100644
--- a/src/JsonObject.cpp
+++ b/src/JsonObject.cpp
@@ -17,7 +17,7 @@ using namespace ArduinoJson::Internals;
 
 JsonObject JsonObject::_invalid(NULL);
 
-JsonObject::node_type *JsonObject::getOrCreateNodeAt(const char *key) {
+JsonObject::node_type *JsonObject::getOrCreateNodeAt(JsonObjectKey key) {
   node_type *existingNode = getNodeAt(key);
   if (existingNode) return existingNode;
 
@@ -25,21 +25,21 @@ JsonObject::node_type *JsonObject::getOrCreateNodeAt(const char *key) {
   return newNode;
 }
 
-JsonArray &JsonObject::createNestedArray(const char *key) {
+JsonArray &JsonObject::createNestedArray(JsonObjectKey key) {
   if (!_buffer) return JsonArray::invalid();
   JsonArray &array = _buffer->createArray();
   set(key, array);
   return array;
 }
 
-JsonObject &JsonObject::createNestedObject(const char *key) {
+JsonObject &JsonObject::createNestedObject(JsonObjectKey key) {
   if (!_buffer) return JsonObject::invalid();
   JsonObject &object = _buffer->createObject();
   set(key, object);
   return object;
 }
 
-JsonObject::node_type *JsonObject::getNodeAt(const char *key) const {
+JsonObject::node_type *JsonObject::getNodeAt(JsonObjectKey key) const {
   for (node_type *node = _firstNode; node; node = node->next) {
     if (!strcmp(node->content.key, key)) return node;
   }
diff --git a/test/ArduinoString_Tests.cpp b/test/ArduinoString_Tests.cpp
new file mode 100644
index 000000000..2aa6c5405
--- /dev/null
+++ b/test/ArduinoString_Tests.cpp
@@ -0,0 +1,109 @@
+// Copyright Benoit Blanchon 2014-2015
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+
+#include <gtest/gtest.h>
+#include <ArduinoJson.h>
+
+TEST(ArduinoStringTests, JsonBuffer_ParseArray) {
+  DynamicJsonBuffer jsonBuffer;
+  String json("[1,2]");
+  JsonArray &array = jsonBuffer.parseArray(json);
+  ASSERT_TRUE(array.success());
+}
+
+TEST(ArduinoStringTests, JsonBuffer_ParseObject) {
+  DynamicJsonBuffer jsonBuffer;
+  String json("{\"a\":1,\"b\":2}");
+  JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_TRUE(object.success());
+}
+
+TEST(ArduinoStringTests, JsonVariant) {
+  String input = "Hello world!";
+  JsonVariant variant(input);
+  ASSERT_TRUE(variant.is<String>());
+  String output = variant.as<String>();
+  ASSERT_EQ(input, output);
+}
+
+TEST(ArduinoStringTests, JsonObject_Subscript) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_STREQ("value", object[String("key")]);
+}
+
+TEST(ArduinoStringTests, JsonObject_ConstSubscript) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  const JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_STREQ("value", object[String("key")]);
+}
+
+TEST(ArduinoStringTests, JsonObject_Set) {
+  DynamicJsonBuffer jsonBuffer;
+  JsonObject &object = jsonBuffer.createObject();
+  String key = "key";
+  object.set(key, "value");
+  ASSERT_STREQ("value", object["key"]);
+}
+
+TEST(ArduinoStringTests, JsonObject_Get) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  const JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_STREQ("value", object.get(String("key")));
+}
+
+TEST(ArduinoStringTests, JsonObject_GetT) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  const JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_STREQ("value", object.get<const char *>(String("key")));
+}
+
+TEST(ArduinoStringTests, JsonObject_IsT) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  const JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_TRUE(object.is<const char *>(String("key")));
+}
+
+TEST(ArduinoStringTests, JsonObject_CreateNestedObject) {
+  DynamicJsonBuffer jsonBuffer;
+  String key = "key";
+  char json[64];
+  JsonObject &object = jsonBuffer.createObject();
+  object.createNestedObject(key);
+  object.printTo(json, sizeof(json));
+  ASSERT_STREQ("{\"key\":{}}", json);
+}
+
+TEST(ArduinoStringTests, JsonObject_CreateNestedArray) {
+  DynamicJsonBuffer jsonBuffer;
+  String key = "key";
+  char json[64];
+  JsonObject &object = jsonBuffer.createObject();
+  object.createNestedArray(key);
+  object.printTo(json, sizeof(json));
+  ASSERT_STREQ("{\"key\":[]}", json);
+}
+
+TEST(ArduinoStringTests, JsonObject_ContainsKey) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  const JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_TRUE(object.containsKey(String("key")));
+}
+
+TEST(ArduinoStringTests, JsonObject_Remove) {
+  DynamicJsonBuffer jsonBuffer;
+  char json[] = "{\"key\":\"value\"}";
+  JsonObject &object = jsonBuffer.parseObject(json);
+  ASSERT_EQ(1, object.size());
+  object.remove(String("key"));
+  ASSERT_EQ(0, object.size());
+}
\ No newline at end of file
diff --git a/test/JsonVariant_Undefined_Tests.cpp b/test/JsonVariant_Undefined_Tests.cpp
index 5d1c7db35..98ef914a4 100644
--- a/test/JsonVariant_Undefined_Tests.cpp
+++ b/test/JsonVariant_Undefined_Tests.cpp
@@ -30,9 +30,25 @@ TEST_F(JsonVariant_Undefined_Tests, AsBoolReturnsFalse) {
 }
 
 TEST_F(JsonVariant_Undefined_Tests, AsArrayReturnInvalid) {
-  EXPECT_EQ(JsonArray::invalid(), variant.asArray());
+  EXPECT_EQ(JsonArray::invalid(), variant.as<JsonArray&>());
+}
+
+TEST_F(JsonVariant_Undefined_Tests, AsConstArrayReturnInvalid) {
+  EXPECT_EQ(JsonArray::invalid(), variant.as<const JsonArray&>());
 }
 
 TEST_F(JsonVariant_Undefined_Tests, AsObjectReturnInvalid) {
+  EXPECT_EQ(JsonObject::invalid(), variant.as<JsonObject&>());
+}
+
+TEST_F(JsonVariant_Undefined_Tests, AsConstObjectReturnInvalid) {
+  EXPECT_EQ(JsonObject::invalid(), variant.as<const JsonObject&>());
+}
+
+TEST_F(JsonVariant_Undefined_Tests, AsArrayWrapperReturnInvalid) {
+  EXPECT_EQ(JsonArray::invalid(), variant.asArray());
+}
+
+TEST_F(JsonVariant_Undefined_Tests, AsObjectWrapperReturnInvalid) {
   EXPECT_EQ(JsonObject::invalid(), variant.asObject());
 }