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3113a52a7d
The at function throws json::out_of_range.403 when a nonexistent object key is provided (just like the usual at function). This was not documented and users could assume json::out_of_range.404 would be thrown instead. - Updated documentation. - Added example code.
104 lines
2.4 KiB
C++
104 lines
2.4 KiB
C++
#include <iostream>
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#include "json.hpp"
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using json = nlohmann::json;
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int main()
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{
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// create a JSON value
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json j =
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{
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{"number", 1}, {"string", "foo"}, {"array", {1, 2}}
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};
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// read-only access
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// output element with JSON pointer "/number"
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std::cout << j.at("/number"_json_pointer) << '\n';
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// output element with JSON pointer "/string"
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std::cout << j.at("/string"_json_pointer) << '\n';
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// output element with JSON pointer "/array"
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std::cout << j.at("/array"_json_pointer) << '\n';
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// output element with JSON pointer "/array/1"
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std::cout << j.at("/array/1"_json_pointer) << '\n';
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// writing access
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// change the string
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j.at("/string"_json_pointer) = "bar";
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// output the changed string
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std::cout << j["string"] << '\n';
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// change an array element
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j.at("/array/1"_json_pointer) = 21;
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// output the changed array
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std::cout << j["array"] << '\n';
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// out_of_range.106
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try
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{
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// try to use an array index with leading '0'
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json::reference ref = j.at("/array/01"_json_pointer);
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}
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catch (json::parse_error& e)
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{
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std::cout << e.what() << '\n';
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}
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// out_of_range.109
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try
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{
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// try to use an array index that is not a number
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json::reference ref = j.at("/array/one"_json_pointer);
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}
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catch (json::parse_error& e)
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{
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std::cout << e.what() << '\n';
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}
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// out_of_range.401
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try
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{
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// try to use a an invalid array index
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json::reference ref = j.at("/array/4"_json_pointer);
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}
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catch (json::out_of_range& e)
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{
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std::cout << e.what() << '\n';
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}
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// out_of_range.402
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try
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{
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// try to use the array index '-'
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json::reference ref = j.at("/array/-"_json_pointer);
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}
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catch (json::out_of_range& e)
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{
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std::cout << e.what() << '\n';
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}
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// out_of_range.403
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try
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{
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// try to use a JSON pointer to an nonexistent object key
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json::const_reference ref = j.at("/foo"_json_pointer);
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}
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catch (json::out_of_range& e)
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{
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std::cout << e.what() << '\n';
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}
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// out_of_range.404
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try
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{
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// try to use a JSON pointer that cannot be resolved
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json::reference ref = j.at("/number/foo"_json_pointer);
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}
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catch (json::out_of_range& e)
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{
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std::cout << e.what() << '\n';
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}
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}
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