c++ - How to parse coinbase api data or Json parser help to understand how this code work bitcoin ticker

Question

I got this piece of code from here.

Basically the part below I have trouble understanding. The data returned by coinbase api have several data sets in it. I don't get how the program parses the Bitcoin price in dollars; having said that: how can I parse other data like the Bitcoin Euro price.

   // We now create a URI for the request
  String url = "/v1/bpi/currentprice.json";
  
  Serial.print("Requesting URL: ");
  Serial.println(url);
  
  // This will send the request to the server
  client.print(String("GET ") + url + " HTTP/1.1
" +
               "Host: " + host + "
" + 
               "Connection: close

");
  delay(100);
  
  // Read all the lines of the reply from server and print them to Serial
  String answer;
  while (client.available()) {
    String line = client.readStringUntil('
');
    answer += line;
  }

  client.stop();
  Serial.println();
  Serial.println("closing connection");

  // Process answer
  Serial.println();
  Serial.println("Answer: ");
  Serial.println(answer);

  // Convert to JSON
  String jsonAnswer;
  int jsonIndex;

  for (int i = 0; i < answer.length(); i++) {
    if (answer[i] == '{') {
      jsonIndex = i;
      break;
    }
  }

  // Get JSON data
  jsonAnswer = answer.substring(jsonIndex);
  Serial.println();
  Serial.println("JSON answer: ");
  Serial.println(jsonAnswer);
  jsonAnswer.trim();

  // Get rate as float
  int rateIndex = jsonAnswer.indexOf("rate_float");
  String priceString = jsonAnswer.substring(rateIndex + 12, rateIndex + 18);
  priceString.trim();
  float price = priceString.toFloat();

Answer 1

等待大神答复