All Versions Of ArduinoJson 6

See the dedicated article: ArduinoJson 6.18: custom converters.

Changes

• Added support for custom converters (issue #687)
• Added support for Printable (issue #1444)
• Removed support for char values, see below (issue #1498)
• deserializeJson() leaves \uXXXX unchanged instead of returning NotSupported
• deserializeMsgPack() inserts null instead of returning NotSupported
• Removed DeserializationError::NotSupported
• Added JsonVariant::is<JsonArrayConst/JsonObjectConst>() (issue #1412)
• Added JsonVariant::is<JsonVariant/JsonVariantConst>() (issue #1412)
• Changed JsonVariantConst::is<JsonArray/JsonObject>() to return false (issue #1412)
• Simplified JsonVariant::as<T>() to always return T (see below)
• Updated folders list in .mbedignore (PR #1515 by @AGlass0fMilk)
• Fixed member-call-on-null-pointer in getMember() when array is empty
• serializeMsgPack(doc, buffer, size) doesn’t add null-terminator anymore (issue #1545)
• serializeJson(doc, buffer, size) adds null-terminator only if there is enough room
• PlatformIO: set build.libArchive to false (PR #1550 by @askreet)

BREAKING CHANGES

Support for char removed

We cannot cast a JsonVariant to a char anymore, so the following will break:

char age = doc["age"]; // error: no matching function for call to 'variantAs(VariantData*&)'

Instead, you must use another integral type, such as int8_t:

int8_t age = doc["age"]; // OK

Similarly, we cannot assign from a char anymore, so the following will break:

char age; doc["age"] = age; // error: no matching function for call to 'VariantRef::set(const char&)'

Instead, you must use another integral type, such as int8_t:

int8_t age; doc["age"] = age; // OK

A deprecation warning with the message “Support for char is deprecated, use int8_t or uint8_t instead” was added to allow a smooth transition.

as<T>() always returns T

Previously, JsonVariant::as<T>() could return a type different from T. The most common example is as<char*>() that returned a const char*. While this feature simplified a few use cases, it was confusing and complicated the implementation of custom converters.

Starting from this version, as<T> doesn’t try to auto-correct the return type and always return T, which means that you cannot write this anymore:

Serial.println(doc["sensor"].as<char*>()); // error: invalid conversion from 'const char*' to 'char*' [-fpermissive]

Instead, you must write:

Serial.println(doc["sensor"].as<const char*>()); // OK

A deprecation warning with the message “Replace as<char*>() with as<const char*>()” was added to allow a smooth transition.

DeserializationError::NotSupported removed

On a different topic, DeserializationError::NotSupported has been removed. Instead of returning this error:

• deserializeJson() leaves \uXXXX unchanged (only when ARDUINOJSON_DECODE_UNICODE is 0)
• deserializeMsgPack() replaces unsupported values with nulls

Const-aware is<T>()

Lastly, a very minor change concerns JsonVariantConst::is<T>(). It used to return true for JsonArray and JsonOject, but now it returns false. Instead, you must use JsonArrayConst and JsonObjectConst.

Download links

• ArduinoJson-v6.18.0.h
• ArduinoJson-v6.18.0.hpp

Online examples

• JsonGeneratorExample.ino
• JsonParserExample.ino
• MsgPackParserExample.ino