json/docs/examples/at__json_pointer_const.cpp
2023-09-23 17:19:50 +02:00

81 lines
1.9 KiB
C++

#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
using namespace nlohmann::literals;
int main()
{
// create a JSON value
const json j =
{
{"number", 1}, {"string", "foo"}, {"array", {1, 2}}
};
// read-only access
// output element with JSON pointer "/number"
std::cout << j.at("/number"_json_pointer) << '\n';
// output element with JSON pointer "/string"
std::cout << j.at("/string"_json_pointer) << '\n';
// output element with JSON pointer "/array"
std::cout << j.at("/array"_json_pointer) << '\n';
// output element with JSON pointer "/array/1"
std::cout << j.at("/array/1"_json_pointer) << '\n';
// out_of_range.109
try
{
// try to use an array index that is not a number
json::const_reference ref = j.at("/array/one"_json_pointer);
}
catch (const json::parse_error& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.401
try
{
// try to use an invalid array index
json::const_reference ref = j.at("/array/4"_json_pointer);
}
catch (const json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.402
try
{
// try to use the array index '-'
json::const_reference ref = j.at("/array/-"_json_pointer);
}
catch (const json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.403
try
{
// try to use a JSON pointer to a nonexistent object key
json::const_reference ref = j.at("/foo"_json_pointer);
}
catch (const json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.404
try
{
// try to use a JSON pointer that cannot be resolved
json::const_reference ref = j.at("/number/foo"_json_pointer);
}
catch (const json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
}