// ArduinoJson - https://arduinojson.org // Copyright © 2014-2022, Benoit BLANCHON // MIT License // // This example shows the different ways you can use String with ArduinoJson. // // Use String objects sparingly, because ArduinoJson duplicates them in the // JsonDocument. Prefer plain old char[], as they are more efficient in term of // code size, speed, and memory usage. // // https://arduinojson.org/v6/example/string/ #include void setup() { DynamicJsonDocument doc(1024); // You can use a String as your JSON input. // WARNING: the string in the input will be duplicated in the JsonDocument. String input = "{\"sensor\":\"gps\",\"time\":1351824120,\"data\":[48.756080,2.302038]}"; deserializeJson(doc, input); // You can use a String as a key to get a member from JsonDocument // No duplication is done. long time = doc[String("time")]; // You can use a String as a key to set a member of a JsonDocument // WARNING: the content of the String will be duplicated in the JsonDocument. doc[String("time")] = time; // You can get the content of a JsonVariant as a String // No duplication is done, at least not in the JsonDocument. String sensor = doc["sensor"]; // Unfortunately, the following doesn't work (issue #118): // sensor = doc["sensor"]; // <- error "ambiguous overload for 'operator='" // As a workaround, you need to replace by: sensor = doc["sensor"].as(); // You can set a String as the content of a JsonVariant // WARNING: the content of the String will be duplicated in the JsonDocument. doc["sensor"] = sensor; // It works with serialized() too: doc["sensor"] = serialized(sensor); // You can also concatenate strings // WARNING: the content of the String will be duplicated in the JsonDocument. doc[String("sen") + "sor"] = String("gp") + "s"; // You can compare the content of a JsonObject with a String if (doc["sensor"] == sensor) { // ... } // Lastly, you can print the resulting JSON to a String // WARNING: it doesn't replace the content but appends to it String output; serializeJson(doc, output); } void loop() { // not used in this example } // See also // -------- // // https://arduinojson.org/ contains the documentation for all the functions // used above. It also includes an FAQ that will help you solve any problem. // // The book "Mastering ArduinoJson" contains a quick C++ course that explains // how your microcontroller stores strings in memory. On several occasions, it // shows how you can avoid String in your program. // Learn more at https://arduinojson.org/book/ // Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤