44 lines
1.2 KiB
C++
44 lines
1.2 KiB
C++
#include <iostream>
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#include <nlohmann/json.hpp>
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using json = nlohmann::json;
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int main()
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{
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json j = json::parse(R"({"name": "Mary", "age": 42})");
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// look up the key, then test the type: neither step throws
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const auto keys = {"name", "age", "city"};
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for (const char* key : keys)
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{
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const auto it = j.find(key);
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if (it == j.end())
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{
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std::cout << key << ": missing\n";
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}
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else if (it->is_string())
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{
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std::cout << key << ": string \"" << it->get_ref<const std::string&>() << "\"\n";
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}
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else
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{
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std::cout << key << ": not a string, but " << it->type_name() << '\n';
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}
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}
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// get_ptr returns a null pointer if the value has another type
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const std::string* name = j["name"].get_ptr<const std::string*>();
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const std::string* age = j["age"].get_ptr<const std::string*>();
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std::cout << "get_ptr<string*>: name = " << (name != nullptr) << ", age = " << (age != nullptr) << '\n';
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// value() is NOT exception-free: it throws if the key exists with a different type
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try
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{
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std::cout << j.value("name", 0) << '\n';
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}
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catch (const json::type_error& 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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