使用nlohmann JSON解析json
使用nlohmann JSON解析json
提问于 2018-02-16 19:22:34
我正在尝试使用nlohmann的json.hpp解析JSON结构。但我不会从字符串创建JSON结构。我已经尝试了所有的方法，但还是失败了。
我的要求是：
1)根据字符串创建JSON结构。
2)从中找到"statusCode“的值。
经过这么长时间的尝试，我真的开始怀疑nlohmann的json解析器是否支持嵌套JSON。
#include "json.hpp"
using namespace std;
int main(){
// giving error 1
nlohmann::json strjson = nlohmann::json::parse({"statusResp":{"statusCode":"S001","message":"Registration Success","snStatus":"Active","warrantyStart":"00000000","warrantyEnd":"00000000","companyBPID":"0002210887","siteBPID":"0002210888","contractStart":"00000000","contractEnd":"00000000"}});
// Giving error 2:
auto j= "{
"statusResp": {
"statusCode": "S001",
"message": "Registration Success",
"snStatus": "Active",
"warrantyStart": "20170601",
"warrantyEnd": "20270601",
"companyBPID": "0002210887",
"siteBPID": "0002210888",
"contractStart": "00000000",
"contractEnd": "00000000"
}
}"_json;
// I actually want to get the value of "statusCode" code from the JSOn structure. But no idea how to parse the nested value.
return 1;
}以下是两种初始化的错误：
//ERROR 1:
test.cpp: In function 'int main()':
test.cpp:17:65: error: expected '}' before ':' token
nlohmann::json strjson = nlohmann::json::parse({"statusResp":{"statusCode":"S001","message":"Registration Success","snStatus":"Active","warrantyStart":"00000000","warrantyEnd":"00000000","companyBPID":"0002210887","siteBPID":"0002210888","contractStart":"00000000","contractEnd":"00000000"}});
// ERROR 2:
hemanty@sLinux:/u/hemanty/workspaces/avac/cb-product/mgmt/framework/src/lib/libcurl_cpp$g++ test.cpp -std=gnu++11
test.cpp: In function 'int main()':
test.cpp:27:17: error: expected '}' before ':' token
"statusResp": {回答 2
Stack Overflow用户
发布于 2018-02-19 19:36:21
因为"是字符串文字的开始和结束字符，所以在字符串中不能有"字符，而不能在其前面放置\。
std::string str = " "statusCode":"5001" "; //This does not work
std::string str = " \"statusCode\":\"5001\" "; //This will work当您想要生成包含大量"的字符串时，一个更简单的替代方法是使用R"" string literal。然后你就可以这样写了。
std::string str = R"("statusCode":"5001")";如果我们现在将此转换为您的json示例，则解析字符串的正确方法将是以下方法之一。
auto j3 = json::parse("{ \"happy\": true, \"pi\": 3.141 }");
// and below the equivalent with raw string literal
auto j3 = json::parse(R"({"happy": true, "pi": 3.141 })");
//Here we use the `_json` suffix
auto j2 = "
{
\"happy\": true,
\"pi\": 3.141
}"_json;
// Here we combine the R"" with _json suffix to do the same thing.
auto j2 = R"(
{
"happy": true,
"pi": 3.141
}
)"_json;取自readme的示例
Stack Overflow用户
发布于 2021-01-29 12:32:07
如果这就是你所需要的：
std::string ss= R"(
{
"test-data":
[
{
"name": "tom",
"age": 11
},
{
"name": "jane",
"age": 12
}
]
}
)";
json myjson = json::parse(ss);
auto &students = myjson["test-data"];
for(auto &student : students) {
cout << "name=" << student["name"].get<std::string>() << endl;
}或者：
json myjson = { {"name", "tom"}, {"age", 11} };
cout << "name=" << myjson["name"].get<std::string>() << endl;页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/48825709
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