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// Illustrates how to read custom data types from JSON files.
#include "caf/actor_system.hpp"
#include "caf/actor_system_config.hpp"
#include "caf/caf_main.hpp"
#include "caf/json_reader.hpp"
#include "caf/type_id.hpp"
#include <fstream>
#include <iostream>
#include <string>
#include <string_view>
constexpr std::string_view example_input = R"([
{
"id": 1,
"name": "John Doe"
},
{
"id": 2,
"name": "Jane Doe",
"email": "jane@doe.com"
}
])";
struct user {
uint32_t id;
std::string name;
std::optional<std::string> email;
};
template <class Inspector>
bool inspect(Inspector& f, user& x) {
return f.object(x).fields(f.field("id", x.id), f.field("name", x.name),
f.field("email", x.email));
}
using user_list = std::vector<user>;
CAF_BEGIN_TYPE_ID_BLOCK(example_app, caf::first_custom_type_id)
CAF_ADD_TYPE_ID(example_app, (user))
CAF_ADD_TYPE_ID(example_app, (user_list))
CAF_END_TYPE_ID_BLOCK(example_app)
int caf_main(caf::actor_system& sys) {
// Get file path from config (positional argument).
auto& cfg = sys.config();
if (cfg.remainder.size() != 1) {
std::cerr << "*** expected one positional argument: path to a JSON file\n";
return EXIT_FAILURE;
}
auto& file_path = cfg.remainder[0];
// Read file into a string.
std::ifstream input{file_path};
if (!input) {
std::cerr << "*** unable to open input file '" << file_path << "'\n";
return EXIT_FAILURE;
}
std::string json{std::istreambuf_iterator<char>{input},
std::istreambuf_iterator<char>{}};
// Parse the JSON-formatted text.
caf::json_reader reader;
if (!reader.load(json)) {
std::cerr << "*** failed to parse JSON input: "
<< to_string(reader.get_error()) << '\n';
return EXIT_FAILURE;
}
// Deserialize our user list from the parsed JSON.
user_list users;
if (!reader.apply(users)) {
std::cerr
<< "*** failed to deserialize the user list: "
<< to_string(reader.get_error())
<< "\n\nNote: expected a JSON list of user objects. For example:\n"
<< example_input << '\n';
return EXIT_FAILURE;
}
// Print the list in "CAF format".
std::cout << "Entries loaded from file:\n";
for (auto& entry : users)
std::cout << "- " << caf::deep_to_string(entry) << '\n';
return EXIT_SUCCESS;
}
CAF_MAIN(caf::id_block::example_app)
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