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<h1 id="use-error-codes"><a class="header" href="err_codes.html#use-error-codes">use error codes</a></h1>
<p>c++ supports error codes and they are good to standardize the tracking errors in programs.</p>
<p>like std::exception; it supports an interface and via it we can provide our custom types. starting with defined enums.</p>
<pre><code class="language-c++">
#include <iostream>
#include <system_error>
enum class MyErrorCodes {
DATABASE_CONNECTION_FAILED = 100,
INVALID_USER_INPUT = 101
};
class MyErrorCategory : public std::error_category {
public:
const char* name() const noexcept override {
return "MyErrorCategory";
}
std::string message(int ev) const override {
switch (static_cast<MyErrorCodes>(ev)) {
case MyErrorCodes::DATABASE_CONNECTION_FAILED:
return "Database connection failed.";
case MyErrorCodes::INVALID_USER_INPUT:
return "Invalid user input.";
default:
return "Unknown error.";
}
}
};
const MyErrorCategory myErrorCategory{};
std::error_code make_error_code(MyErrorCodes e) {
return {static_cast<int>(e), myErrorCategory};
}
int main() {
std::error_code ec1 = make_error_code(MyErrorCodes::DATABASE_CONNECTION_FAILED);
std::error_code ec2 = std::make_error_code(MyErrorCodes::INVALID_USER_INPUT);
std::cout << "Error 1: " << ec1.message() << std::endl;
std::cout << "Error 2: " << ec2.message() << std::endl;
return 0;
}
</code></pre>
<p>or use stds</p>
<pre><code class="language-c++">#include <iostream>
#include <fstream>
#include <system_error>
std::error_code readFile(const std::string& filename) {
std::ifstream file(filename);
if (!file.is_open()) {
return std::make_error_code(std::errc::no_such_file_or_directory);
}
// ... read file content ...
if(file.fail()){
return std::make_error_code(std::errc::io_error);
}
return {}; // No error
}
int main() {
std::error_code ec = readFile("my_file.txt");
if (ec) {
std::cerr << "Error: " << ec.message() << std::endl;
} else {
std::cout << "File read successfully." << std::endl;
}
return 0;
}
</code></pre>
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