Recursively entering Json object based on string

Question

I've got the following json object:

{
    "ESP_IN_PC_OUT":{
        "track":{
            "1":{
                "mute":{
                    "type":"LED",
                    "pins":[4]
                }
            },
            "2":{
                "mute":{
                    "type":"LED",
                    "pins":[5]
                }
            }
        }
    }
}

I want to enter the object, depending on a string of the format "/index1/index2/index3 ..." (The string is the address of an OSC message). For example, "/track/2/mute" should return a Json object like this:

{
    "type":"LED",
    "pins":[5]
}

So that I can access the type, the pins array, and some other values that will be implemented later.

I'm using the Arduino JSON library on an ESP8266. This is the code I've tried:

#include <ArduinoJson.h>

char *jsonstr = "{\n    \"ESP_IN_PC_OUT\":{\n        \"track\":{\n            \"1\":{\n                \"mute\":{\n                    \"type\":\"LED\",\n                    \"pins\":[4]\n                }\n            },\n            \"2\":{\n                \"mute\":{\n                    \"type\":\"LED\",\n                    \"pins\":[5]\n                }\n            }\n        }\n    },\n\n\n    \"ESP_OUT_PC_IN\":{\n        \"analog\":{\n        },\n        \"digital\":{\n            \"16\":\"/track/1/mute\"\n        }\n    }\n}"; 

void setup() {
  Serial.begin(115200);

  DynamicJsonBuffer jsonBuffer;

  JsonObject& root = jsonBuffer.parseObject(jsonstr);
  if (!root.success()) {
    Serial.println("parseObject() failed");
    return;
  }

  Serial.println((const char*) root["ESP_IN_PC_OUT"]["track"]["2"]["mute"]["type"]); // prints "LED"
  Serial.println();

  char *address = "/track/2/mute";     // _____Interesting part_____
  char *tmp = strtok(address,"/");
  JsonObject& tmpJson = root["ESP_IN_PC_OUT"];
  bool success = true;
  while(tmp != NULL && success == true){
    Serial.println(tmp);
    if(tmpJson.containsKey(tmp)){
      tmpJson = tmpJson[tmp];        // Error: use of deleted function 'ArduinoJson::JsonObject& ArduinoJson::JsonObject::operator=(const ArduinoJson::JsonObject&)'
      tmp = strtok(NULL,"/");
    } else {
      success = false;
    }
  }
  if(success == true){
    Serial.println((const char*)tmpJson["type"]);
  } else {
    Serial.println("Address not found");
  }
}

void loop() {
}

However, this gives me the following error message:

JSON_OSC_settings2:26: error: use of deleted function 'ArduinoJson::JsonObject& ArduinoJson::JsonObject::operator=(const ArduinoJson::JsonObject&)'

       tmpJson = tmpJson[tmp];

               ^

In file included from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.hpp:12:0,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\JSON_OSC_settings2\JSON_OSC_settings2.ino:1:

C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson/JsonObject.hpp:38:7: note: 'ArduinoJson::JsonObject& ArduinoJson::JsonObject::operator=(const ArduinoJson::JsonObject&)' is implicitly deleted because the default definition would be ill-formed:

 class JsonObject : public Internals::JsonPrintable<JsonObject>,

       ^

In file included from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson/JsonArray.hpp:13:0,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.hpp:11,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\JSON_OSC_settings2\JSON_OSC_settings2.ino:1:

C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson/Internals/ReferenceType.hpp:32:18: error: 'ArduinoJson::Internals::ReferenceType& ArduinoJson::Internals::ReferenceType::operator=(const ArduinoJson::Internals::ReferenceType&)' is private

   ReferenceType& operator=(const ReferenceType&);

                  ^

In file included from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.hpp:12:0,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/ArduinoJson.h:8,

                 from C:\Users\Pieter\Documents\Arduino\JSON_OSC_settings2\JSON_OSC_settings2.ino:1:

C:\Users\Pieter\Documents\Arduino\libraries\ArduinoJson-master/include/ArduinoJson/JsonObject.hpp:38:7: error: within this context

 class JsonObject : public Internals::JsonPrintable<JsonObject>,

       ^

exit status 1
use of deleted function 'ArduinoJson::JsonObject& ArduinoJson::JsonObject::operator=(const ArduinoJson::JsonObject&)'

How can I solve this? What different approach could I take?

Answer 1

I am not a C developer but what could help you is called »JSONPath«, which is meant to be the counterpart of xPath for JSON. Probably you can find a library which can do that.

This seems to be a similar thing.