JsonDocument::add()
Description
When the JsonDocument contains an array, JsonDocument::add() appends a value to the array.
When the JsonDocument contains a value that is not an array, JsonDocument::add() does nothing.
When the JsonDocument is empty, JsonDocument::add() converts the JsonDocument to an array containing one element.
This feature allows creating an array without calling JsonDocument::to<JsonArray(). For example the two following snippets are equivalent:
JsonArray arr = doc.to<JsonArray>();
arr.add(42);
doc.clear();
doc.add(42);
Signatures
bool add(bool value);
bool add(float value);
bool add(double value);
bool add(signed char value);
bool add(signed long value);
bool add(signed int value);
bool add(signed short value);
bool add(unsigned char value);
bool add(unsigned long value);
bool add(unsigned int value);
bool add(unsigned short value);
bool add(char *value); // stores a copy
bool add(const char *value); // stores a pointer ⚠️
bool add(const __FlashStringHelper *value); // stores a copy
bool add(const String &value); // stores a copy
bool add(const std::string &value); // stores a copy
bool add(const Printable& value); // stores a copy
bool add(std::string_view value); // stores a copy
bool add(JsonArray array); // stores a deep copy
bool add(JsonObject object); // stores a deep copy
bool add(JsonVariant variant); // stores a deep copy
bool add(const JsonDocument& doc); // stores a deep copy
bool add(TEnum value); // alias of add(int)
bool add(T value); // calls user-defined function
Arguments
value: the value of to append to the array, it can be any type supported by ArduinoJson.
All types are stored by copy, except const char* which is stored by pointer.
Return value
JsonDocument::add() returns a bool that tells whether the operation was successful or not:
trueif the value was successfully added.falseif there was not enough memory in theJsonDocument.
Example
StaticJsonDocument<200> doc;
array.add("hello"); // null -> ["hello"]
array.add(3.14156); // ["hello"] -> ["hello",3.14156]
serializeJson(doc, Serial);
will write
["hello",3.14156]
