C++怎么往json字符串中写入内容

要将内容写入JSON字符串，你需要使用一个 JSON 库。以下是使用 RapidJSON 库将内容写入JSON字符串的示例代码：

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

using namespace rapidjson;
using namespace std;

int main() {
    // 创建 JSON 对象
    Document document;
    document.SetObject();

    // 往 JSON 对象中添加数据
    Value name;
    name.SetString("John", document.GetAllocator());
    document.AddMember("name", name, document.GetAllocator());

    Value age;
    age.SetInt(30);
    document.AddMember("age", age, document.GetAllocator());

    Value address;
    address.SetObject();
    Value street;
    street.SetString("123 Main St.", document.GetAllocator());
    Value city;
    city.SetString("Anytown", document.GetAllocator());
    Value state;
    state.SetString("CA", document.GetAllocator());
    address.AddMember("street", street, document.GetAllocator());
    address.AddMember("city", city, document.GetAllocator());
    address.AddMember("state", state, document.GetAllocator());
    document.AddMember("address", address, document.GetAllocator());

    // 生成 JSON 字符串
    StringBuffer buffer;
    Writer<StringBuffer> writer(buffer);
    document.Accept(writer);

    // 输出 JSON 字符串
    cout << buffer.GetString() << endl;

    return 0;
}

输出结果如下：

{"name":"John","age":30,"address":{"street":"123 Main St.","city":"Anytown","state":"CA"}}

你可以根据你的需求修改代码中的数据，以生成符合你要求的 JSON 字符串。