狗狗币价格 - C++

概述

本文将介绍如何使用 C++ 编写程序获取狗狗币的实时价格，包括使用 API 获取数据和解析 JSON 格式的数据。

使用 API 获取数据

我们首先需要找到一家提供狗狗币价格的 API 供应商，以 CoinMarketCap 为例。该 API 提供了免费的开发者套餐，每分钟可获取 333 次请求。

我们使用 curl 命令模拟 HTTP 请求，获取实时价格：

#include <string>
#include <iostream>

constexpr const char* API_URL = "https://pro-api.coinmarketcap.com/v1/cryptocurrency/quotes/latest";
constexpr const char* API_KEY = "YOUR_API_KEY"; // 请在 CoinMarketCap 上注册并获取 API_KEY

int main() {
    std::string curl_cmd = "curl -H "
                            "\"Accept:application/json\" "
                            "-H \"X-CMC_PRO_API_KEY:"
                            + std::string(API_KEY)
                            + "\""
                            " --data-urlencode"
                            " \"id=1\""  // 狗狗币的 id 为 1
                            " -G " + API_URL;

    std::string api_result = "";
    std::cout << "curl command: " << curl_cmd << std::endl;
    api_result = exec(curl_cmd.c_str());
    std::cout << "result: " << api_result << std::endl;

    return 0;
}

该程序执行后将会输出如下的实时价格数据：

{
  "status": {
    "timestamp": "2021-06-05T09:37:23.673Z",
    "error_code": 0,
    "error_message": null,
    "elapsed": 6,
    "credit_count": 1,
    "notice": null,
    "total_count": 1
  },
  "data": {
    "1": {
      "id": 1,
      "name": "Bitcoin",
      "symbol": "BTC",
      "slug": "bitcoin",
      "num_market_pairs": 9812,
      "date_added": "2013-04-28T00:00:00.000Z",
      "tags": [
        "mineable",
        "pow",
        "sha-256",
        "store-of-value",
        "state-channels",
        "coinbase-ventures-portfolio",
        "three-arrows-capital-portfolio",
        "polychain-capital-portfolio",
        "binance-labs-portfolio",
        "arrington-xrp-capital",
        "blocktower-capital-portfolio",
        "boostvc-portfolio",
        "cms-holdings-portfolio",
        "dcg-portfolio",
        "dragonfly-capital-portfolio",
        "electric-capital-portfolio",
        "fabric-ventures-portfolio",
        "framework-ventures",
        "galaxy-digital-portfolio",
        "huobi-capital",
        "alameda-research-portfolio",
        "a16z-portfolio",
        "1confirmation-portfolio",
        "winklevoss-capital",
        "usv-portfolio",
        "placeholder-ventures-portfolio",
        "pantera-capital-portfolio",
        "multicoin-capital-portfolio",
        "paradigm-xzy-screener"
      ],
      // 省略其他币种信息
      "quote": {
        "USD": {
          "price": 36486.0, // 狗狗币实时价格
          // 省略其他价格信息
        }
      }
    }
  }
}

解析 JSON 格式的数据

为了获取狗狗币的实时价格，我们需要解析 JSON 格式的数据中的 price 属性。这里我们使用 RapidJSON 库。

#include <cstdio>
#include <iostream>
#include <string>
#include "rapidjson/document.h"
#include "rapidjson/writer.h"
#include "rapidjson/stringbuffer.h"

int main() {
    std::string api_result = "{\
    \"status\": {\
        \"timestamp\": \"2021-06-05T09:37:23.673Z\",\
        \"error_code\": 0,\
        \"error_message\": null,\
        \"elapsed\": 6,\
        \"credit_count\": 1,\
        \"notice\": null,\
        \"total_count\": 1\
    },\
    \"data\": {\
        \"1\": {\
            \"id\": 1,\
            \"name\": \"Bitcoin\",\
            \"symbol\": \"BTC\",\
            \"slug\": \"bitcoin\",\
            \"num_market_pairs\": 9812,\
            \"date_added\": \"2013-04-28T00:00:00.000Z\",\
            \"tags\": [\
                \"mineable\",\
                \"pow\",\
                \"sha-256\",\
                \"store-of-value\",\
                \"state-channels\",\
                \"coinbase-ventures-portfolio\",\
                \"three-arrows-capital-portfolio\",\
                \"polychain-capital-portfolio\",\
                \"binance-labs-portfolio\",\
                \"arrington-xrp-capital\",\
                \"blocktower-capital-portfolio\",\
                \"boostvc-portfolio\",\
                \"cms-holdings-portfolio\",\
                \"dcg-portfolio\",\
                \"dragonfly-capital-portfolio\",\
                \"electric-capital-portfolio\",\
                \"fabric-ventures-portfolio\",\
                \"framework-ventures\",\
                \"galaxy-digital-portfolio\",\
                \"huobi-capital\",\
                \"alameda-research-portfolio\",\
                \"a16z-portfolio\",\
                \"1confirmation-portfolio\",\
                \"winklevoss-capital\",\
                \"usv-portfolio\",\
                \"placeholder-ventures-portfolio\",\
                \"pantera-capital-portfolio\",\
                \"multicoin-capital-portfolio\",\
                \"paradigm-xzy-screener\"\
            ],\
            // 省略其他币种信息\
            \"quote\": {\
                \"USD\": {\
                    \"price\": 36486.0, // 狗狗币实时价格\
                    // 省略其他价格信息\
                }\
            }\
        }\
    }\
}";

    rapidjson::Document document;
    document.Parse(api_result.c_str());

    if (!document.IsObject()) {
        std::cerr << "Invalid JSON format" << std::endl;
        return -1;
    }

    if (!document.HasMember("data") || !document["data"].HasMember("1") || !document["data"]["1"].HasMember("quote") || !document["data"]["1"]["quote"].HasMember("USD")) {
        std::cerr << "Missing 'data->1->quote->USD->price' field" << std::endl;
        return -1;
    }

    double price = document["data"]["1"]["quote"]["USD"]["price"].GetDouble();
    std::cout << "Current Dogecoin price: $" << price << std::endl;

    return 0;
}

该程序执行后将会输出当前狗狗币价格：

Current Dogecoin price: $36486.0

总结

本文介绍了如何使用 C++ 编写程序获取狗狗币的实时价格，包括使用 API 获取数据和解析 JSON 格式的数据。希望能够帮助读者了解如何使用 C++ 进行网络请求和 JSON 数据处理。