ArduinoJson

When reporting a problem or opening a new issue on GitHub, ensure you provide the following information to receive a fast and helpful response:

• Good title: A clear, descriptive summary of the issue.
• Short description: A concise explanation of the problem.
• Target platform: The hardware or environment you are using.
• Compiler model and version: The specific compiler being used.
• MVCE: A Minimal Viable Code Example (a small, self-contained piece of code that reproduces the issue).
• Compiler output: The full error messages or logs produced by the compiler.

Before asking for help with ArduinoJson, follow these steps to find a solution:

1. Consult the FAQ.
2. Search the API Reference for technical details.

If the answer is not found, you can create a new issue on GitHub.

Use serializeJson() to convert a JsonDocument into a JSON string or to write it to a stream (like Serial).

JsonDocument doc;

doc["sensor"] = "gps";
doc["time"]   = 1351824120;
doc["data"][0] = 48.756080;
doc["data"][1] = 2.302038;

serializeJson(doc, Serial);
// This prints: 
// {"sensor":"gps","time":1351824120,"data":[48.756080,2.302038]}

Use deserializeJson() to parse a JSON string or stream into a JsonDocument. Once parsed, you can access values using the [] operator with keys or indices.

const char* json = "{\"sensor\":\"gps\",\"time\":1351824120,\"data\":[48.756080,2.302038]}";

JsonDocument doc;
deserializeJson(doc, json);

const char* sensor = doc["sensor"];
long time          = doc["time"];
double latitude    = doc["data"][0];
double longitude   = doc["data"][1];

The following configuration macros have been removed and should be deleted from your project configuration or build flags:

• ARDUINOJSON_SLOT_OFFSET_SIZE: Use ARDUINOJSON_SLOT_ID_SIZE instead.
• ARDUINOJSON_ENABLE_STRING_DEDUPLICATION: This feature is now always enabled and the macro is no longer needed.

If you are using legacy classes from ArduinoJson 5, you will encounter compilation errors or deprecation warnings. To resolve these, you should migrate to the new API. Specifically, classes like StaticJsonBuffer, DynamicJsonBuffer, JsonBuffer, and RawJson are no longer supported and will trigger a compilation error.

For a detailed migration guide, visit: https://arduinojson.org/v7/upgrade-from-v5/

The containsKey(key) method is deprecated. Instead of checking for a key directly on the variant, use the subscript operator followed by an .is<T>() check.

Recommended Pattern:

// Instead of:
if (obj.containsKey("key")) { ... }

// Use:
if (obj["key"].is<T>()) { ... }

If a JsonVariant represents an object, you can modify it using these methods:

• operator[](key): Accesses or modifies a member using a string key.
• remove(key): Removes a member from the object using a string key.
• to<T>(): Converts the variant into an empty JsonObject (if T is JsonObject).

The JsonVariant class (which inherits from VariantRefBase) provides a mutable interface for interacting with JSON values, objects, and arrays. You can use it to check types, cast values, set new values, and manipulate nested structures.

Key Operations:

• Type Checking: Use .is<T>() to check if a value matches a specific type.
• Casting: Use .as<T>() to cast a value to a specific type.
• Setting Values: Use .set(value) to copy a value into the variant.
• Clearing: Use .clear() to set the value to null.
• Metadata: Use .size() for the number of elements/members and .nesting() for the depth of the value.