Can't support convert the type? std::string json_str = R"({"value": "3.1415"})"; float value = j["value"].get<float>();

[TerryHoCQ]

Description

include

include

include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() { std::string json_str = R"({"value": "3.1415"})"; json j = json::parse(json_str);

float value = j["value"].get<float>();
std::cout << "Value: " << value << std::endl;

std::string float_str = "3.1415926";
float float_num = std::stof(float_str);
std::cout << "Float: " << float_num << std::endl;

return 0;

}

Reproduction steps

include

include

include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() { std::string json_str = R"({"value": "3.1415"})"; json j = json::parse(json_str);

float value = j["value"].get<float>();
std::cout << "Value: " << value << std::endl;

std::string float_str = "3.1415926";
float float_num = std::stof(float_str);
std::cout << "Float: " << float_num << std::endl;

return 0;

}

Expected vs. actual results

include

include

include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() { std::string json_str = R"({"value": "3.1415"})"; json j = json::parse(json_str);

float value = j["value"].get<float>();
std::cout << "Value: " << value << std::endl;

std::string float_str = "3.1415926";
float float_num = std::stof(float_str);
std::cout << "Float: " << float_num << std::endl;

return 0;

}

Minimal code example

#include <iostream>
#include <string>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main() {
    std::string json_str = R"({"value": "3.1415"})";
    json j = json::parse(json_str);

    float value = j["value"].get<float>();
    std::cout << "Value: " << value << std::endl;

    std::string float_str = "3.1415926";
    float float_num = std::stof(float_str);
    std::cout << "Float: " << float_num << std::endl;

    return 0;
}

Error messages

No response

Compiler and operating system

vs20019+WIN10

Library version

v3.11.2

Validation

• [ ] The bug also occurs if the latest version from the develop branch is used.
• [ ] I can successfully compile and run the unit tests.

[nlohmann]

In order to asses your issue, we need the following information:

• What is the issue you have?

• Please describe the steps to reproduce the issue. Can you provide a small but working code example?

• What is the expected behavior?

• And what is the actual behavior instead?

• Which compiler and operating system are you using? Is it a supported compiler?

• Did you use a released version of the library or the version from the develop branch?

• If you experience a compilation error: can you compile and run the unit tests?

[TerryHoCQ]

float value = j["value"].get<float>();

float value = j["value"].get(); //this will throw exception, the original type in JSON TXT R"({"value": "3.1415"})" is string, we try to convert string to a float.

[nlohmann]

The library does not provide string-to-float conversion.