All versions of ArduinoJson 5

• Fixed warning “unused variable” with GCC 4.4 (issue #912)
• Fixed warning “maybe uninitialized” (issue #909)
• Added an clear message for StaticJsonDocument, DynamicJsonDocument…

• Removed spurious files in the Particle library

• Improved float serialization when -fsingle-precision-constant is used
• Fixed JsonVariant::is<int>() that returned true for empty strings
• Fixed JsonVariant::is<String>() (closes #763)

• Fixed JsonBuffer::parse() not respecting nesting limit correctly (issue #693)
• Fixed inconsistencies in nesting level counting (PR #695 from Zhenyu Wu)
• Fixed null values that could be pass to strcmp() (PR #745 from Mike Karlesky)
• Added macros ARDUINOJSON_VERSION, ARDUINOJSON_VERSION_MAJOR…

• Fixed JsonVariant::operator|(int) that returned the default value if the variant contained a double (issue #675)
• Allowed non-quoted key to contain underscores (issue #665

• Changed the rules of string duplication (issue #658)
• RawJson() accepts any kind of string and obeys to the same rules for duplication
• Changed the return type of strdup() to const char* to prevent double duplication
• Marked strdup() as deprecated

New rules for string duplication

type	duplication
const char*	no
char*	no yes
String	yes
std::string	yes
const __FlashStringHelper*	yes

These new rules make JsonBuffer::strdup() useless.

• Added JsonVariant::operator| to return a default value (see below)
• Added a clear error message when compiled as C instead of C++ (issue #629)
• Added detection of MPLAB XC compiler (issue #629)
• Added detection of Keil ARM Compiler (issue #629)
• Added an example that shows how to save and load a configuration file
• Reworked all other examples

How to use the new feature?

If you have a block like this:

const char* ssid = root["ssid"];
if (!ssid)
  ssid = "default ssid";

You can simplify like that:

const char* ssid = root["ssid"] | "default ssid";

• Fixed DynamicJsonBuffer::clear() not resetting allocation size (issue #561)
• Fixed incorrect rounding for float values (issue #588)

• Removed dependency on PGM_P as Particle 0.6.2 doesn’t define it (issue #546)
• Fixed warning “dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]”
• Fixed warning “floating constant exceeds range of ‘float’ [-Woverflow]” (issue #544)
• Fixed warning “this statement may fall through” [-Wimplicit-fallthrough=] (issue #539)
• Removed ARDUINOJSON_DOUBLE_IS_64BITS as it became useless.
• Fixed too many decimals places in float serialization (issue #543)

• Made JsonBuffer non-copyable (PR #524 by @luisrayas3)
• Added StaticJsonBuffer::clear()
• Added DynamicJsonBuffer::clear()

• Fixed IntelliSense errors in Visual Micro (issue #483)
• Fixed compilation in IAR Embedded Workbench (issue #515)
• Fixed reading “true” as a float (issue #516)
• Added ARDUINOJSON_DOUBLE_IS_64BITS
• Added ARDUINOJSON_EMBEDDED_MODE

• Removed configurable number of decimal places (issues #288, #427 and #506)
• Changed exponentiation thresholds to 1e7 and 1e-5 (issues #288, #427 and #506)
• JsonVariant::is<double>() now returns true for integers
• Fixed error IsBaseOf is not a member of ArduinoJson::TypeTraits (issue #495)
• Fixed error forming reference to reference (issue #495)

BREAKING CHANGES

Old syntax	New syntax
double_with_n_digits(3.14, 2)	3.14
float_with_n_digits(3.14, 2)	3.14f
obj.set("key", 3.14, 2)	obj["key"] = 3.14
arr.add(3.14, 2)	arr.add(3.14)

Input	Old output	New output
3.14159	3.14	3.14159
42.0	42.00	42
0.0	0.00	0

Expression	Old result	New result
JsonVariant(42).is<int>()	true	true
JsonVariant(42).is<float>()	false	true
JsonVariant(42).is<double>()	false	true

• Added JsonArray::remove(iterator) (issue #479)
• Added JsonObject::remove(iterator)
• Renamed JsonArray::removeAt(size_t) into remove(size_t)
• Renamed folder include/ to src/
• Fixed warnings floating constant exceeds range of floatand floating constant truncated to zero (issue #483)
• Removed Print class and converted printTo() to a template method (issue #276)
• Removed example IndentedPrintExample.ino
• Now compatible with Particle 0.6.1, thanks to Jacob Nite (issue #294 and PR #461 by @foodbag)

• Added custom implementation of strtod() (issue #453)
• Added custom implementation of strtol() (issue #465)
• char is now treated as an integral type (issue #337, #370)

• Fixed an access violation in DynamicJsonBuffer when memory allocation fails (issue #433)
• Added operators == and != for two JsonVariants (issue #436)
• Fixed JsonVariant::operator[const FlashStringHelper*] (issue #441)

• Fixed parsing of comments (issue #421)
• Fixed ignored Stream timeout (issue #422)
• Made sure we don’t read more that necessary (issue #422)
• Fixed error when the key of a JsonObject is a char[] (issue #423)
• Reduced code size when using const references
• Fixed error with string of type unsigned char* (issue #428)
• Added deprecated attribute on asArray(), asObject() and asString() (issue #420)

• Fixed error when assigning a volatile int to a JsonVariant (issue #415)
• Fixed errors with Variable Length Arrays (issue #416)
• Fixed error when both ARDUINOJSON_ENABLE_STD_STREAM and ARDUINOJSON_ENABLE_ARDUINO_STREAM are set to 1
• Fixed error “Stream does not name a type” (issue #412)

• Added operator == to compare JsonVariant and strings (issue #402)
• Added support for Stream (issue #300)
• Reduced memory consumption by not duplicating spaces and comments

BREAKING CHANGES

JsonBuffer::parseObject() and JsonBuffer::parseArray() have been pulled down to the derived classes DynamicJsonBuffer and StaticJsonBufferBase.

This means that if you have code like:

void myFunction(JsonBuffer& jsonBuffer);

you need to replace it with one of the following:

void myFunction(DynamicJsonBuffer& jsonBuffer);
void myFunction(StaticJsonBufferBase& jsonBuffer);
template<typename TJsonBuffer> void myFunction(TJsonBuffer& jsonBuffer);

• Added an printTo(char[N]) and prettyPrintTo(char[N]) (issue #292)
• Added ability to set a nested value like this: root["A"]["B"] = "C" (issue #352)
• Renamed *.ipp to *Impl.hpp because they were ignored by Arduino IDE (issue #396)

• Made PROGMEM available on more platforms (issue #381)
• Fixed PROGMEM causing an exception on ESP8266 (issue #383)

• Added support for PROGMEM (issue #76)
• Fixed compilation error when index is not an int (issue #381)

• Templatized all functions using String or std::string
• Removed ArduinoJson::String
• Removed JsonVariant::defaultValue<T>()
• Removed non-template JsonObject::get() and JsonArray.get()
• Fixed support for StringSumHelper (issue #184)
• Replaced ARDUINOJSON_USE_ARDUINO_STRING by ARDUINOJSON_ENABLE_STD_STRING and ARDUINOJSON_ENABLE_ARDUINO_STRING (issue #378)
• Added example StringExample.ino to show where String can be used
• Increased default nesting limit to 50 when compiled for a computer (issue #349)

BREAKING CHANGES

The non-template functions JsonObject::get() and JsonArray.get() have been removed. This means that you need to explicitely tell the type you expect in return.

Old code:

#define ARDUINOJSON_USE_ARDUINO_STRING 0
JsonVariant value1 = myObject.get("myKey");
JsonVariant value2 = myArray.get(0);

New code:

#define ARDUINOJSON_ENABLE_ARDUINO_STRING 0
#define ARDUINOJSON_ENABLE_STD_STRING 1
JsonVariant value1 = myObject.get<JsonVariant>("myKey");
JsonVariant value2 = myArray.get<JsonVariant>(0);

• Fixed array[idx].as<JsonVariant>() and object[key].as<JsonVariant>()
• Fixed return value of JsonObject::set() (issue #350)
• Fixed undefined behavior in Prettyfier and Print (issue #354)
• Fixed parser that incorrectly rejected floats containing a + (issue #349)

• Fixed -Wparentheses warning introduced in v5.6.5 (PR #335 by @nuket)
• Added .mbedignore for ARM mbdeb (PR #334 by @nuket)
• Fixed JsonVariant::success() which didn’t propagate JsonArray::success() nor JsonObject::success() (issue #342).

• as<char*>() now returns true when input is null (issue #330)

• Fixed error in float serialization (issue #324)

• Improved speed of float serialization (about twice faster)
• Added as<JsonArray>() as a synonym for as<JsonArray&>()… (issue #291)
• Fixed call of overloaded isinf(double&) is ambiguous (issue #284)

• Fixed build when another lib does #undef isnan (issue #284)

• Added missing #pragma once (issue #310)

• ArduinoJson is now a header-only library (issue #199)

• Fixed compilation error with Intel Galileo (issue #299)

• Added JsonVariant::success() (issue #279)
• Renamed JsonVariant::invalid<T>() to JsonVariant::defaultValue<T>()

• Changed ::String to ArduinoJson::String (issue #275)
• Changed ::Print to ArduinoJson::Print too

• Added custom implementation of ftoa (issues #266, #267, #269 and #270)
• Added JsonVariant JsonBuffer::parse() (issue #265)
• Fixed unsigned long printed as signed long (issue #170)

• Added JsonVariant::as<char*>() as a synonym for JsonVariant::as<const char*>() (issue #257)
• Added example JsonHttpClient (issue #256)
• Added JsonArray::copyTo() and JsonArray::copyFrom() (issue #254)
• Added RawJson() to insert pregenerated JSON portions (issue #259)

• Removed String duplication when one replaces a value in a JsonObject (PR #232 by @ulion)

• Added support of long long (issue #171)
• Moved all build settings to ArduinoJson/Configuration.hpp

BREAKING CHANGE

If you defined ARDUINOJSON_ENABLE_STD_STREAM, you now need to define it to 1.

• Made the library compatible with PlatformIO (issue #181)
• Fixed JsonVariant::is<bool>() that was incorrectly returning false (issue #214)

• Made library easier to use from a CMake project: simply add_subdirectory(ArduinoJson/src)
• Changed String to be a typedef of std::string (issues #142 and #161)

BREAKING CHANGES

• JsonVariant(true).as<String>() now returns "true" instead of "1"
• JsonVariant(false).as<String>() now returns "false" instead of "0"

• Added parameter to DynamicJsonBuffer constructor to set initial size (issue #152)
• Fixed warning about library category in Arduino 1.6.6 (issue #147)
• Examples: Added a loop to wait for serial port to be ready (issue #156)

• Added overload JsonObjectSuscript::set(value, decimals) (issue #143)
• Use float instead of double to reduce the size of JsonVariant (issue #134)

• Fixed ambiguous overload with JsonArraySubscript and JsonObjectSubscript (issue #122)

• Fixed printTo(String) which wrote numbers instead of strings (issue #120)
• Fixed return type of JsonArray::is<T>() and some others (issue #121)

• Fixed segmentation fault in parseObject(String) and parseArray(String), when the StaticJsonBuffer is too small to hold a copy of the string
• Fixed Clang warning “register specifier is deprecated” (issue #102)
• Fixed GCC warning “declaration shadows a member” (issue #103)
• Fixed memory alignment, which made ESP8266 crash (issue #104)
• Fixed compilation on Visual Studio 2010 and 2012 (issue #107)

• Fixed compilation with Arduino 1.0.6 (issue #99)

• Added support of String class (issues #55, #56, #70, #77)
• Added JsonBuffer::strdup() to make a copy of a string (issues #10, #57)
• Implicitly call strdup() for String but not for char* (issues #84, #87)
• Added support of non standard JSON input (issue #44)
• Added support of comments in JSON input (issue #88)
• Added implicit cast between numerical types (issues #64, #69, #93)
• Added ability to read number values as string (issue #90)
• Redesigned JsonVariant to leverage converting constructors instead of assignment operators (issue #66)
• Switched to new the library layout (requires Arduino 1.0.6 or above)

BREAKING CHANGES

• JsonObject::add() was renamed to set()
• 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 predictable. You certainly don’t want that in an embedded environment!