Added DeserializationOption::Filter (closes #959)

examples/JsonFilterExample/JsonFilterExample.ino

@@ -0,0 +1,66 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2020
+// MIT License
+//
+// This example shows how to use DeserializationOpion::Filter
+//
+// https://arduinojson.org/v6/example/filter/
+
+#include <ArduinoJson.h>
+
+void setup() {
+  // Initialize serial port
+  Serial.begin(9600);
+  while (!Serial) continue;
+
+  // The huge input: an extract from OpenWeatherMap response
+  const __FlashStringHelper* input_json = F(
+      "{\"cod\":\"200\",\"message\":0,\"list\":[{\"dt\":1581498000,\"main\":{"
+      "\"temp\":3.23,\"feels_like\":-3.63,\"temp_min\":3.23,\"temp_max\":4.62,"
+      "\"pressure\":1014,\"sea_level\":1014,\"grnd_level\":1010,\"humidity\":"
+      "58,\"temp_kf\":-1.39},\"weather\":[{\"id\":800,\"main\":\"Clear\","
+      "\"description\":\"clear "
+      "sky\",\"icon\":\"01d\"}],\"clouds\":{\"all\":0},\"wind\":{\"speed\":6."
+      "19,\"deg\":266},\"sys\":{\"pod\":\"d\"},\"dt_txt\":\"2020-02-12 "
+      "09:00:00\"},{\"dt\":1581508800,\"main\":{\"temp\":6.09,\"feels_like\":-"
+      "1.07,\"temp_min\":6.09,\"temp_max\":7.13,\"pressure\":1015,\"sea_"
+      "level\":1015,\"grnd_level\":1011,\"humidity\":48,\"temp_kf\":-1.04},"
+      "\"weather\":[{\"id\":800,\"main\":\"Clear\",\"description\":\"clear "
+      "sky\",\"icon\":\"01d\"}],\"clouds\":{\"all\":9},\"wind\":{\"speed\":6."
+      "64,\"deg\":268},\"sys\":{\"pod\":\"d\"},\"dt_txt\":\"2020-02-12 "
+      "12:00:00\"}],\"city\":{\"id\":2643743,\"name\":\"London\",\"coord\":{"
+      "\"lat\":51.5085,\"lon\":-0.1257},\"country\":\"GB\",\"population\":"
+      "1000000,\"timezone\":0,\"sunrise\":1581492085,\"sunset\":1581527294}}");
+
+  // The filter: it contains "true" for each value we want to keep
+  const __FlashStringHelper* filter_json =
+      F("{\"list\":[{\"dt\":true,\"main\":{\"temp\":true}]}");
+
+  // Create the filter document
+  StaticJsonDocument<200> filter;
+  deserializeJson(filter, filter_json);
+
+  // Deserialize the document
+  StaticJsonDocument<400> doc;
+  deserializeJson(doc, input_json, DeserializationOption::Filter(filter));
+
+  // Print the result
+  serializeJsonPretty(doc, Serial);
+}
+
+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
+// deserialization problem.
+//
+// The book "Mastering ArduinoJson" contains a tutorial on deserialization.
+// It begins with a simple example, like the one above, and then adds more
+// features like deserializing directly from a file or an HTTP request.
+// Learn more at https://arduinojson.org/book/
+// Use the coupon code TWENTY for a 20% discount ❤❤❤❤❤