ArduinoJson: F.A.Q

Error: invalid conversion from 'const char*' to 'int' [-fpermissive]

Let’s say you have the following JSON to parse:

{
  "modules": [
    {
      "name": "hello",
      "id": 10
    },
    {
      "name": "world",
      "id": 20
    }
  ]
}

If you write the following program:

JsonObject& root =  jsonBuffer.parseOject(input);
JsonArray& modules = root["modules"];

const char* name = modules["hello"][0];

You’ll get the following compilation error:

error: invalid conversion from 'const char*' to 'size_t {aka unsigned int}' [-fpermissive]

This is because modules is an array of object, as such it’s indexed by an integer, not by a string.

The solution is:

const char* name = modules[0]["hello"];

See:

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