C ++:使用nlohmann json从文件中读取json对象 [英] C++: Reading a json object from file with nlohmann json
问题描述
我正在使用nlohmann的json库在c ++中处理json对象.最终,我想从文件中读取一个json对象,例如这样的简单对象.
I am using the nlohmann's json library to work with json objects in c++. Ultimately, I'd like to read a json object from a file, e.g. a simple object like this.
{
"happy": true,
"pi": 3.141
}
我不太确定该如何处理.在 https://github.com/nlohmann 处,给出了几种从字符串文字反序列化的方法,但实际上并没有.将其扩展为读取文件似乎微不足道.有人对此有经验吗?
I'm not quite sure how to approach this. At https://github.com/nlohmann several ways are given to deserialise from a string literal, however it doesn't seem trivial to extend this to read in a file. Does anyone have experience with this?
推荐答案
2017年3月3日更新 适用于现代C ++版本3的JSON
自版本3.0 起,不推荐使用json::json(std::ifstream&)
.人们应该使用
Update 2017-07-03 for JSON for Modern C++ version 3
Since version 3.0, json::json(std::ifstream&)
is deprecated. One should use json::parse()
instead:
std::ifstream ifs("{\"json\": true}");
json j = json::parse(ifs);
JSON for Modern C ++ version 2的更新
Update for JSON for Modern C++ version 2
Since version 2.0, json::operator>>() id deprecated
. One should use json::json()
instead:
std::ifstream ifs("{\"json\": true}");
json j(ifs);
现代C ++版本1的 JSON的原始答案
使用json::operator>>(std::istream&)
:
Original answer for JSON for Modern C++ version 1
Use json::operator>>(std::istream&)
:
json j;
std::ifstream ifs("{\"json\": true}");
ifs >> j;
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