Arduino Json object reuse

Using Arduino Programming Questions
1

Hey guys Im working on a project that make HTTP calls to a API.
This API returns a JSON. And I was using the Arduino JSON library but I ran into a problem.

I think I cant write over the data in the JSON object.

I have a for loop, and I make x numbers of calls to the API with a different parameter.
The respone I want to save in a JSON object, then copy the result into a typedef struct and then work from there.

I have the following function:

void requestHandler::requestFromApi(String coinId, namePriceTimeStruct *namePriceTimeStruct, uint8_t debug){
    if (Serial){
        Serial.println("Class requestHandler, function: requestFromApi");
    }
    String completPath = REQUEST_ADDRESS_API + coinId;
    static char buffer[64];
    if (Serial && debug){
        sprintf(buffer,"Making request to %s", completPath.c_str());
        Serial.println(buffer); 
    }
    String payload;
    HTTPClient http;
    http.begin(clientHttpCall, completPath); 
    int httpCode = http.GET(); 
    if (httpCode > 0) { 
      payload = http.getString();  // When I print this, the request is succesfull.
    }
    http.end();


    JsonObject filter_data = filter.createNestedObject("data");
    filter_data["id"] = true;
    filter_data["price"] = true;
    filter_data["price_timestamp"] = true;

    DeserializationError error = deserializeJson(doc, payload, DeserializationOption::Filter(filter));

    if (error) {
        if (Serial){
            Serial.print(F("deserializeJson() failed: "));
            Serial.println(error.f_str());
        }
    } else{
        namePriceTimeStruct->idCoin = doc["data"]["id"].as<String>();
        namePriceTimeStruct->priceCoin =  doc["data"]["price"].as<String>();
        String correctDate = doc["data"]["price_timestamp"].as<String>();
        correctDate.replace("Z", "");
        namePriceTimeStruct->timeStamp = correctDate;
        static char buffer[64];
        if (Serial && debug){
            sprintf(buffer,"data struct %s, %s, %s", namePriceTimeStruct->idCoin, namePriceTimeStruct->priceCoin, namePriceTimeStruct->timeStamp);
            Serial.println(buffer); 
            sprintf(buffer,"data json %s, %s, %s", doc["data"]["id"].as<String>(), doc["data"]["price"].as<String>(), doc["data"]["price_timestamp"].as<String>());
            Serial.println(buffer); 
        }
    }
}

This is the Serial.print.. With the first try is works good, then the second one there is nothing in the JSON object. Is there something Im missing with the JSON object / class, or should i do it another way.

Class requestHandler, function: requestFromApi
Making request to http://api.iot.hva-robots.nl/crypto/ADA
data struct ADA, 1.93019129, 2021-11-10T10:51:00
data json ADA, 1.93019129, 2021-11-10T10:51:00
Class requestHandler, function: requestInsertDataCoin
Making call to URL: http://oege.ie.hva.nl:8112/insert/data/ADA/2021-11-10T10:51:00/1.93019129

Class requestHandler, function: requestFromApi
Making request to http://api.iot.hva-robots.nl/crypto/BNB
data struct null, null, null
data json null, null, null
Class requestHandler, function: requestInsertDataCoin
Making call to URL: http://oege.ie.hva.nl:8112/insert/data/null/null/null

Class requestHandler, function: requestFromApi
Making request to http://api.iot.hva-robots.nl/crypto/BTC
data struct null, null, null
data json null, null, null
2

It looks as though you are calling two different APIs and expecting a similar JSON object from them both. What do you get if you send the second request manually from a browser or postman?

3

The request have the same JSON response. I just need to flush out all the data in the JSON object in the code so I can fill it again.

4

Are you SURE the next JSON string will be available when you call requestHandler::requestFromApi() on every iteration of your 'for' loop? What if it's not available yet? Then 'httpCode' will not be >0 so 'payload' will be an empty String that you attempt to deserialize any way:

image

No way for us to tell how the 'for' loop works since you didn't bother to post complete code.

5

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