JsonVariant::add()

Description

When the JsonVariant points to an array, JsonVariant::add() appends a value to the array. Otherwise, this function does nothing.

In other words, JsonVariant::add() reproduces JsonArray::add().

Signatures

bool add(bool value) const;

bool add(float value) const;
bool add(double value) const;

bool add(signed char value) const;
bool add(signed long value) const;
bool add(signed int value) const;
bool add(signed short value) const;
bool add(unsigned char value) const;
bool add(unsigned long value) const;
bool add(unsigned int value) const;
bool add(unsigned short value) const;

bool add(char *value) const;                       // stores a copy
bool add(const char *value) const;                 // stores a pointer ⚠️
bool add(const __FlashStringHelper *value) const;  // stores a copy

bool add(const String &value) const;       // stores a copy
bool add(const std::string &value) const;  // stores a copy
bool add(const Printable& value) const;    // stores a copy
bool add(std::string_view value) const;    // stores a copy

bool add(JsonArray array) const;          // stores a deep copy
bool add(JsonObject object) const;        // stores a deep copy
bool add(JsonVariant variant) const;      // stores a deep copy
bool add(const JsonDocument& doc) const;  // stores a deep copy

bool add(TEnum value) const;  // alias of add(int)
bool add(T value) const;      // calls user-defined function

Arguments

value: the value to append to the array.

All types are stored by copy, except const char* which is stored by pointer.

Return value

JsonVariant::add() returns a bool that tells whether the operation was successful or not:

  • true if the value was successfully added.
  • false if there was not enough memory in the JsonDocument

User-defined types 🆕

JsonVariant::add() supports user-defined types by calling convertToJson(). For example, to support tm, you must define:

bool convertToJson(const tm& src, JsonVariant dst) {
  char buf[32];
  strftime(buf, sizeof(buf), "%FT%TZ", &src);
  return dst.set(buf);
}

This feature was added in ArduinoJson 6.18.0, see article for details.

See also