我正在尝试创建一个可以在C ++的REST API控制台中显示JSON文件的程序。我正在尝试从api.trello.com获取JSON文件，但我遇到的每个示例都给出了一个错误，通常是关于@Query＆amp; cbegin()以及它不是cend() ...
这是我的代码：
web::json::value我在VS 2015中遇到此错误。
唯一的错误是// The code includes the most frequently used includes necessary to work with C++ REST SDK
#include "cpprest/containerstream.h"
#include "cpprest/filestream.h"
#include "cpprest/http_client.h"
#include "cpprest/json.h"
#include "cpprest/producerconsumerstream.h"
#include <iostream>
#include <sstream>
#include <stdio.h>
#include <stdlib.h>
using namespace ::pplx;
using namespace utility;
using namespace concurrency::streams;
using namespace web;
using namespace web::http;
using namespace web::http::client;
using namespace web::json;
using namespace std;
using namespace web;
using namespace web::http;
using namespace web::http::client;
// Retrieves a JSON value from an HTTP request.
pplx::task<void> RequestJSONValueAsync()
{
// TODO: To successfully use this example, you must perform the request
// against a server that provides JSON data.
// This example fails because the returned Content-Type is text/html and not application/json.
http_client client(L"website.com/theRealURLContainsSecretKeys");
return client.request(methods::GET).then([](http_response response) -> pplx::task<json::value>
{
if (response.status_code() == status_codes::OK)
{
return response.extract_json();
}
// Handle error cases, for now return empty json value...
return pplx::task_from_result(json::value());
})
.then([](pplx::task<json::value> previousTask)
{
try
{
const json::value& v = previousTask.get();
// Perform actions here to process the JSON value...
}
catch (const http_exception& e)
{
// Print error.
wostringstream ss;
ss << e.what() << endl;
wcout << ss.str();
}
});
/* Output:
Content-Type must be application/json to extract (is: text/html)
*/
}
// Demonstrates how to iterate over a JSON object.
void IterateJSONValue()
{
// Create a JSON object.
json::value obj;
obj[L"key1"] = json::value::boolean(false);
obj[L"key2"] = json::value::number(44);
obj[L"key3"] = json::value::number(43.6);
obj[L"key4"] = json::value::string(U("str"));
// Loop over each element in the object.
for (auto iter = obj.cbegin(); iter != obj.cend(); ++iter)
{
// Make sure to get the value as const reference otherwise you will end up copying
// the whole JSON value recursively which can be expensive if it is a nested object.
const json::value &str = iter->first;
const json::value &v = iter->second;
// Perform actions here to process each string and value in the JSON object...
std::wcout << L"String: " << str.as_string() << L", Value: " << v.to_string() << endl;
}
/* Output:
String: key1, Value: false
String: key2, Value: 44
String: key3, Value: 43.6
String: key4, Value: str
*/
}
int wmain()
{
// This example uses the task::wait method to ensure that async operations complete before the app exits.
// In most apps, you typically don�t wait for async operations to complete.
wcout << L"Calling RequestJSONValueAsync..." << endl;
RequestJSONValueAsync().wait();
wcout << L"Calling IterateJSONValue..." << endl;
//IterateJSONValue();
system("pause");
}
我的问题是什么？我该如何解决？
答案 0 :(得分：5)
json::value不包含成员函数cbegin()。如果您访问obj.as_object()或obj.as_array()，则会找到您的开始/结束成员。
// Loop over each element in the object.
for (const auto &pr : obj.as_object()) {
std::wcout << L"String: " << pr.first << L", Value: " << pr.second << endl;
}