JSONCPP 有一个编写器,但它似乎所做的只是从解析器获取信息,然后将其输出到字符串或流中。如何让它改变或创建新的对象、数组、值、字符串等并将它们写入文件?
5 回答
#include<json/writer.h>
代码:
Json::Value event;
Json::Value vec(Json::arrayValue);
vec.append(Json::Value(1));
vec.append(Json::Value(2));
vec.append(Json::Value(3));
event["competitors"]["home"]["name"] = "Liverpool";
event["competitors"]["away"]["code"] = 89223;
event["competitors"]["away"]["name"] = "Aston Villa";
event["competitors"]["away"]["code"]=vec;
std::cout << event << std::endl;
输出:
{
"competitors" :
{
"away" :
{
"code" : [ 1, 2, 3 ],
"name" : "Aston Villa"
},
"home" :
{
"name" : "Liverpool"
}
}
}
#include <json.h>
#include <iostream>
#include <fstream>
void main()
{
std::ofstream file_id;
op_file_id.open("file.txt");
Json::Value value_obj;
//populate 'value_obj' with the objects, arrays etc.
Json::StyledWriter styledWriter;
file_id << styledWriter.write(value_obj);
file_id.close();
}
AFAICT,您创建 Json::Value 类型的对象,该对象适用于所有 JSON 数据类型,并将结果传递给 Json::Writer(具体来说,它的派生类型之一),或简单地传递给流。
例如:将三个整数的数组写入文件:
Json::Value vec(Json::arrayValue);
vec.append(Json::Value(1));
vec.append(Json::Value(2));
vec.append(Json::Value(3));
std::cout << vec;
Json::StyledWriter
已弃用,您可以使用Json::StreamWriterBuilder
将 json 写入文件。
Json::Value rootJsonValue;
rootJsonValue["foo"] = "bar";
Json::StreamWriterBuilder builder;
builder["commentStyle"] = "None";
builder["indentation"] = " ";
std::unique_ptr<Json::StreamWriter> writer(builder.newStreamWriter());
std::ofstream outputFileStream("/tmp/test.json");
writer -> write(rootJsonValue, &outputFileStream);
json 将被写入/tmp/test.json
.
$ cat /tmp/test.json
{
"foo" : "bar"
}
First, you have to create the desired JSON::Value
. You should look at all the constructors (first). To create the necessary hierarchies, see append
and the operator[] overloads; there are overloads for both array indices and string keys for objects.
One way to write the JSON value back out is using StyledStreamWriter::write
and ofstream
.
See cegprakash's answer for how to write it.