json/doc/examples/at_json_pointer.cpp
Niels Lohmann 504012a3db
📝 cleanup after #650
As <iostream> is not included in json.hpp any more, all code examples need to include <iostream> now.
2017-07-09 11:51:38 +02:00

93 lines
2.1 KiB
C++

#include <iostream>
#include "json.hpp"
using json = nlohmann::json;
int main()
{
// create a JSON value
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';
// writing access
// change the string
j.at("/string"_json_pointer) = "bar";
// output the changed string
std::cout << j["string"] << '\n';
// change an array element
j.at("/array/1"_json_pointer) = 21;
// output the changed array
std::cout << j["array"] << '\n';
// out_of_range.106
try
{
// try to use an array index with leading '0'
json::reference ref = j.at("/array/01"_json_pointer);
}
catch (json::parse_error& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.109
try
{
// try to use an array index that is not a number
json::reference ref = j.at("/array/one"_json_pointer);
}
catch (json::parse_error& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.401
try
{
// try to use a an invalid array index
json::reference ref = j.at("/array/4"_json_pointer);
}
catch (json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
// out_of_range.402
try
{
// try to use the array index '-'
json::reference ref = j.at("/array/-"_json_pointer);
}
catch (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::reference ref = j.at("/number/foo"_json_pointer);
}
catch (json::out_of_range& e)
{
std::cout << e.what() << '\n';
}
}