Add getMemberConst() and getElementConst()

src/ArduinoJson/Array/ArrayRef.hpp

@@ -106,10 +106,10 @@ class ArrayConstRef : public ArrayRefBase<const CollectionData>,
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t index) const {
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
     return VariantConstRef(_data ? _data->getElement(index) : 0);
   }
 };
@@ -170,6 +170,11 @@ class ArrayRef : public ArrayRefBase<CollectionData>,
     return VariantRef(_pool, _data ? _data->getElement(index) : 0);
   }
 
+  // Gets the value at the specified index.
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
+    return VariantConstRef(_data ? _data->getElement(index) : 0);
+  }
+
   // Removes element at specified position.
   FORCE_INLINE void remove(iterator it) const {
     if (!_data)

src/ArduinoJson/Array/ElementProxy.hpp

@@ -61,12 +61,20 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
   }
 
   FORCE_INLINE bool isNull() const {
-    return getUpstreamElement().isNull();
+    return getUpstreamElementConst().isNull();
   }
 
   template <typename T>
-  FORCE_INLINE typename enable_if<!is_same<T, char*>::value, T>::type as()
+  FORCE_INLINE typename enable_if<!is_same<T, char*>::value &&
-      const {
+                                      !ConverterNeedsWriteableRef<T>::value,
+                                  T>::type
+  as() const {
+    return getUpstreamElementConst().template as<T>();
+  }
+
+  template <typename T>
+  FORCE_INLINE typename enable_if<ConverterNeedsWriteableRef<T>::value, T>::type
+  as() const {
     return getUpstreamElement().template as<T>();
   }
 
@@ -79,14 +87,23 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
 
   template <typename T>
   FORCE_INLINE operator T() const {
-    return getUpstreamElement();
+    return as<T>();
   }
 
   template <typename T>
-  FORCE_INLINE bool is() const {
+  FORCE_INLINE
+      typename enable_if<ConverterNeedsWriteableRef<T>::value, bool>::type
+      is() const {
     return getUpstreamElement().template is<T>();
   }
 
+  template <typename T>
+  FORCE_INLINE
+      typename enable_if<!ConverterNeedsWriteableRef<T>::value, bool>::type
+      is() const {
+    return getUpstreamElementConst().template is<T>();
+  }
+
   template <typename T>
   FORCE_INLINE typename VariantTo<T>::type to() const {
     return getOrAddUpstreamElement().template to<T>();
@@ -111,15 +128,15 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
 
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor& visitor) const {
-    return getUpstreamElement().accept(visitor);
+    return getUpstreamElementConst().accept(visitor);
   }
 
   FORCE_INLINE size_t size() const {
-    return getUpstreamElement().size();
+    return getUpstreamElementConst().size();
   }
 
   FORCE_INLINE size_t memoryUsage() const {
-    return getUpstreamElement().memoryUsage();
+    return getUpstreamElementConst().memoryUsage();
   }
 
   template <typename TNestedKey>
@@ -132,6 +149,16 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getUpstreamElement().getMember(key);
   }
 
+  template <typename TNestedKey>
+  VariantConstRef getMemberConst(TNestedKey* key) const {
+    return getUpstreamElementConst().getMemberConst(key);
+  }
+
+  template <typename TNestedKey>
+  VariantConstRef getMemberConst(const TNestedKey& key) const {
+    return getUpstreamElementConst().getMemberConst(key);
+  }
+
   template <typename TNestedKey>
   VariantRef getOrAddMember(TNestedKey* key) const {
     return getOrAddUpstreamElement().getOrAddMember(key);
@@ -150,6 +177,10 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getOrAddUpstreamElement().getElement(index);
   }
 
+  VariantConstRef getElementConst(size_t index) const {
+    return getUpstreamElementConst().getElementConst(index);
+  }
+
   VariantRef getOrAddElement(size_t index) const {
     return getOrAddUpstreamElement().getOrAddElement(index);
   }
@@ -178,12 +209,16 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return _array.getElement(_index);
   }
 
+  FORCE_INLINE VariantConstRef getUpstreamElementConst() const {
+    return _array.getElementConst(_index);
+  }
+
   FORCE_INLINE VariantRef getOrAddUpstreamElement() const {
     return _array.getOrAddElement(_index);
   }
 
   friend void convertToJson(const this_type& src, VariantRef dst) {
-    dst.set(src.getUpstreamElement());
+    dst.set(src.getUpstreamElementConst());
   }
 
   TArray _array;

src/ArduinoJson/Document/JsonDocument.hpp

@@ -140,14 +140,14 @@ class JsonDocument : public Visitable,
   // containsKey(const __FlashStringHelper*) const
   template <typename TChar>
   bool containsKey(TChar* key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // containsKey(const std::string&) const
   // containsKey(const String&) const
   template <typename TString>
   bool containsKey(const TString& key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // operator[](const std::string&)
@@ -175,7 +175,7 @@ class JsonDocument : public Visitable,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       operator[](const TString& key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 
   // operator[](char*) const
@@ -185,7 +185,7 @@ class JsonDocument : public Visitable,
   FORCE_INLINE
       typename enable_if<IsString<TChar*>::value, VariantConstRef>::type
       operator[](TChar* key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 
   FORCE_INLINE ElementProxy<JsonDocument&> operator[](size_t index) {
@@ -193,14 +193,14 @@ class JsonDocument : public Visitable,
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
   FORCE_INLINE VariantRef getElement(size_t index) {
     return VariantRef(&_pool, _data.getElement(index));
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t index) const {
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
     return VariantConstRef(_data.getElement(index));
   }
 
@@ -208,20 +208,20 @@ class JsonDocument : public Visitable,
     return VariantRef(&_pool, _data.getOrAddElement(index, &_pool));
   }
 
-  // JsonVariantConst getMember(char*) const
+  // JsonVariantConst getMemberConst(char*) const
-  // JsonVariantConst getMember(const char*) const
+  // JsonVariantConst getMemberConst(const char*) const
-  // JsonVariantConst getMember(const __FlashStringHelper*) const
+  // JsonVariantConst getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar* key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
     return VariantConstRef(_data.getMember(adaptString(key)));
   }
 
-  // JsonVariantConst getMember(const std::string&) const
+  // JsonVariantConst getMemberConst(const std::string&) const
-  // JsonVariantConst getMember(const String&) const
+  // JsonVariantConst getMemberConst(const String&) const
   template <typename TString>
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
-      getMember(const TString& key) const {
+      getMemberConst(const TString& key) const {
     return VariantConstRef(_data.getMember(adaptString(key)));
   }
 

src/ArduinoJson/Object/MemberProxy.hpp

@@ -6,6 +6,7 @@
 
 #include <ArduinoJson/Configuration.hpp>
 #include <ArduinoJson/Polyfills/type_traits.hpp>
+#include <ArduinoJson/Variant/Converter.hpp>
 #include <ArduinoJson/Variant/VariantOperators.hpp>
 #include <ArduinoJson/Variant/VariantRef.hpp>
 #include <ArduinoJson/Variant/VariantShortcuts.hpp>
@@ -35,7 +36,7 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
       : _object(src._object), _key(src._key) {}
 
   FORCE_INLINE operator VariantConstRef() const {
-    return getUpstreamMember();
+    return getUpstreamMemberConst();
   }
 
   FORCE_INLINE this_type &operator=(const this_type &src) {
@@ -64,12 +65,20 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
   }
 
   FORCE_INLINE bool isNull() const {
-    return getUpstreamMember().isNull();
+    return getUpstreamMemberConst().isNull();
   }
 
   template <typename T>
-  FORCE_INLINE typename enable_if<!is_same<T, char *>::value, T>::type as()
+  FORCE_INLINE typename enable_if<!is_same<T, char *>::value &&
-      const {
+                                      !ConverterNeedsWriteableRef<T>::value,
+                                  T>::type
+  as() const {
+    return getUpstreamMemberConst().template as<T>();
+  }
+
+  template <typename T>
+  FORCE_INLINE typename enable_if<ConverterNeedsWriteableRef<T>::value, T>::type
+  as() const {
     return getUpstreamMember().template as<T>();
   }
 
@@ -82,20 +91,29 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
 
   template <typename T>
   FORCE_INLINE operator T() const {
-    return getUpstreamMember();
+    return as<T>();
   }
 
-  template <typename TValue>
+  template <typename T>
-  FORCE_INLINE bool is() const {
+  FORCE_INLINE
-    return getUpstreamMember().template is<TValue>();
+      typename enable_if<ConverterNeedsWriteableRef<T>::value, bool>::type
+      is() const {
+    return getUpstreamMember().template is<T>();
+  }
+
+  template <typename T>
+  FORCE_INLINE
+      typename enable_if<!ConverterNeedsWriteableRef<T>::value, bool>::type
+      is() const {
+    return getUpstreamMemberConst().template is<T>();
   }
 
   FORCE_INLINE size_t size() const {
-    return getUpstreamMember().size();
+    return getUpstreamMemberConst().size();
   }
 
   FORCE_INLINE size_t memoryUsage() const {
-    return getUpstreamMember().memoryUsage();
+    return getUpstreamMemberConst().memoryUsage();
   }
 
   FORCE_INLINE void remove(size_t index) const {
@@ -137,7 +155,7 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
 
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor &visitor) const {
-    return getUpstreamMember().accept(visitor);
+    return getUpstreamMemberConst().accept(visitor);
   }
 
   FORCE_INLINE VariantRef addElement() const {
@@ -148,6 +166,10 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return getUpstreamMember().getElement(index);
   }
 
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
+    return getUpstreamMemberConst().getElementConst(index);
+  }
+
   FORCE_INLINE VariantRef getOrAddElement(size_t index) const {
     return getOrAddUpstreamMember().getOrAddElement(index);
   }
@@ -167,6 +189,21 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return getUpstreamMember().getMember(key);
   }
 
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
+    return getUpstreamMemberConst().getMemberConst(key);
+  }
+
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE VariantConstRef getMemberConst(const TString &key) const {
+    return getUpstreamMemberConst().getMemberConst(key);
+  }
+
   // getOrAddMember(char*) const
   // getOrAddMember(const char*) const
   // getOrAddMember(const __FlashStringHelper*) const
@@ -187,12 +224,16 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     return _object.getMember(_key);
   }
 
+  FORCE_INLINE VariantConstRef getUpstreamMemberConst() const {
+    return _object.getMemberConst(_key);
+  }
+
   FORCE_INLINE VariantRef getOrAddUpstreamMember() const {
     return _object.getOrAddMember(_key);
   }
 
   friend void convertToJson(const this_type &src, VariantRef dst) {
-    dst.set(src.getUpstreamMember());
+    dst.set(src.getUpstreamMemberConst());
   }
 
   TObject _object;

src/ArduinoJson/Object/ObjectImpl.hpp

@@ -40,14 +40,14 @@ template <typename TObject>
 template <typename TString>
 inline typename enable_if<IsString<TString>::value, bool>::type
 ObjectShortcuts<TObject>::containsKey(const TString& key) const {
-  return !impl()->getMember(key).isUnbound();
+  return !impl()->getMemberConst(key).isUnbound();
 }
 
 template <typename TObject>
 template <typename TChar>
 inline typename enable_if<IsString<TChar*>::value, bool>::type
 ObjectShortcuts<TObject>::containsKey(TChar* key) const {
-  return !impl()->getMember(key).isUnbound();
+  return !impl()->getMemberConst(key).isUnbound();
 }
 
 template <typename TObject>

src/ArduinoJson/Object/ObjectRef.hpp

@@ -81,7 +81,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   // containsKey(const String&) const
   template <typename TString>
   FORCE_INLINE bool containsKey(const TString& key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
   // containsKey(char*) const
@@ -89,22 +89,22 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   // containsKey(const __FlashStringHelper*) const
   template <typename TChar>
   FORCE_INLINE bool containsKey(TChar* key) const {
-    return !getMember(key).isUnbound();
+    return !getMemberConst(key).isUnbound();
   }
 
-  // getMember(const std::string&) const
+  // getMemberConst(const std::string&) const
-  // getMember(const String&) const
+  // getMemberConst(const String&) const
   template <typename TString>
-  FORCE_INLINE VariantConstRef getMember(const TString& key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(const TString& key) const {
-    return get_impl(adaptString(key));
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
   }
 
-  // getMember(char*) const
+  // getMemberConst(char*) const
-  // getMember(const char*) const
+  // getMemberConst(const char*) const
-  // getMember(const __FlashStringHelper*) const
+  // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar* key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
-    return get_impl(adaptString(key));
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
   }
 
   // operator[](const std::string&) const
@@ -113,7 +113,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       operator[](const TString& key) const {
-    return get_impl(adaptString(key));
+    return getMemberConst(key);
   }
 
   // operator[](char*) const
@@ -123,7 +123,7 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   FORCE_INLINE
       typename enable_if<IsString<TChar*>::value, VariantConstRef>::type
       operator[](TChar* key) const {
-    return get_impl(adaptString(key));
+    return getMemberConst(key);
   }
 
   FORCE_INLINE bool operator==(ObjectConstRef rhs) const {
@@ -143,10 +143,6 @@ class ObjectConstRef : public ObjectRefBase<const CollectionData>,
   }
 
  private:
-  template <typename TAdaptedString>
-  FORCE_INLINE VariantConstRef get_impl(TAdaptedString key) const {
-    return VariantConstRef(objectGetMember(_data, key));
-  }
 };
 
 class ObjectRef : public ObjectRefBase<CollectionData>,
@@ -207,6 +203,21 @@ class ObjectRef : public ObjectRefBase<CollectionData>,
     return VariantRef(_pool, objectGetMember(_data, adaptString(key)));
   }
 
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE VariantConstRef getMemberConst(const TString& key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
+  }
+
+  // getMemberConst(char*) const
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE VariantConstRef getMemberConst(TChar* key) const {
+    return VariantConstRef(objectGetMember(_data, adaptString(key)));
+  }
+
   // getOrAddMember(const std::string&) const
   // getOrAddMember(const String&) const
   template <typename TString>

src/ArduinoJson/Variant/Converter.hpp

@@ -14,4 +14,7 @@ template <typename T1, typename T2>
 class InvalidConversion;  // Error here? See https://arduinojson.org/v6/invalid-conversion/
 // clang-format on
 
+template <typename T>
+struct ConverterNeedsWriteableRef;
+
 }  // namespace ARDUINOJSON_NAMESPACE

src/ArduinoJson/Variant/VariantRef.hpp

@@ -123,27 +123,27 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
     return as<T>();
   }
 
-  FORCE_INLINE VariantConstRef getElement(size_t index) const {
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
     return VariantConstRef(_data != 0 ? _data->getElement(index) : 0);
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
-    return getElement(index);
+    return getElementConst(index);
   }
 
-  // getMember(const std::string&) const
+  // getMemberConst(const std::string&) const
-  // getMember(const String&) const
+  // getMemberConst(const String&) const
   template <typename TString>
-  FORCE_INLINE VariantConstRef getMember(const TString &key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(const TString &key) const {
     return VariantConstRef(
         objectGetMember(variantAsObject(_data), adaptString(key)));
   }
 
-  // getMember(char*) const
+  // getMemberConst(char*) const
-  // getMember(const char*) const
+  // getMemberConst(const char*) const
-  // getMember(const __FlashStringHelper*) const
+  // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
-  FORCE_INLINE VariantConstRef getMember(TChar *key) const {
+  FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
     const CollectionData *obj = variantAsObject(_data);
     return VariantConstRef(obj ? obj->getMember(adaptString(key)) : 0);
   }
@@ -154,7 +154,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       operator[](const TString &key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 
   // operator[](char*) const
@@ -164,7 +164,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   FORCE_INLINE
       typename enable_if<IsString<TChar *>::value, VariantConstRef>::type
       operator[](TChar *key) const {
-    return getMember(key);
+    return getMemberConst(key);
   }
 };
 
@@ -292,6 +292,10 @@ class VariantRef : public VariantRefBase<VariantData>,
     return VariantRef(_pool, _data != 0 ? _data->getElement(index) : 0);
   }
 
+  FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
+    return VariantConstRef(_data != 0 ? _data->getElement(index) : 0);
+  }
+
   FORCE_INLINE VariantRef getOrAddElement(size_t index) const {
     return VariantRef(_pool, variantGetOrAddElement(_data, index, _pool));
   }
@@ -313,6 +317,22 @@ class VariantRef : public VariantRefBase<VariantData>,
                       _data != 0 ? _data->getMember(adaptString(key)) : 0);
   }
 
+  // getMemberConst(const char*) const
+  // getMemberConst(const __FlashStringHelper*) const
+  template <typename TChar>
+  FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
+  }
+
+  // getMemberConst(const std::string&) const
+  // getMemberConst(const String&) const
+  template <typename TString>
+  FORCE_INLINE
+      typename enable_if<IsString<TString>::value, VariantConstRef>::type
+      getMemberConst(const TString &key) const {
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
+  }
+
   // getOrAddMember(char*) const
   // getOrAddMember(const char*) const
   // getOrAddMember(const __FlashStringHelper*) const