Concatenated Names

[Lenbus]

I like to utilize ArduinoJSON as a tool for parameter management as I can load params from a file and also can access the parameters via their names e.g. via Serial Communication, e.g. sending "location_lat= 42.0" and my script can adjust the variable calling somthing like doc["location_lat"] = 42.0. That way I can try a whole lot of values for all params on the fly, without re-compiling all the time or using tedious potentiometer reads.

Describe the solution you'd like
I'd really like to take this a step further by also accessing nested objects by a single string-key such as "location.lat = 42.0", which should call doc["location"]["lat"] in the background (maybe there is even a more appropriate delimter than '.'). This should of course work for writing and reading.
I'm pretty sure that this should be quite easy to implement, but I did not manage to implement it myself.

The code necessary for that might look something like this:

// NOTE: This is non-tested Pseudo-Code
String key = "location.lat"
float val = 42.0

String delim = "."
int delim_idx = key.indexOf(delim);

if (delim_idx == -1) { return this[key] }

String key0 = key.substring(0, delim_idx );
String key1 = key.substring(delim_idx + 1);

return this[key0][key1] = val    // Note: if key1 still contains delim-chars, recursion should handle that

Additional context
Moreover: is there any way to implicitly save the var type inside the doc as well?
That way I could call: "Serial << doc["lat"]<< endl;" instead of: "Serial << doc["lat"].as<float>() << endl;"

Regards and let me know, what you think. Keep on the phenomenal work! 😊👍

[bblanchon]

Hi,

This request is similar to #821, only simpler.
In your case, the following function should be enough:

JsonVariant resolveJsonPath(JsonVariant variant, const char* path) {
  for (size_t n = 0; path[n]; n++) {
    if (path[n] == '.') {
      variant = variant[JsonString(path, n)];
      path += n + 1;
      n = 0;
    }
  }
  return variant[path];
}

Usage:

// read
double lat = resolveJsonPath(doc, "location.lat");

// write
resolveJsonPath(doc, "location.lat").set(42);

Best regards,
Benoit