example3_destructor_in_RAII.cpp

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#include <iostream>
#include <fstream>
#include <stdexcept>

class FileHandler {
private:
    std::ofstream file;

public:
    FileHandler(const std::string& filename) {
        file.open(filename);
        if (!file.is_open()) {
            throw std::runtime_error("Unable to open file");
        }
        std::cout << "File opened" << std::endl;
    }

    ~FileHandler() {
        if (file.is_open()) {
            file.close();
            std::cout << "File closed" << std::endl;
        }
    }

    void write(const std::string& data) {
        file << data;
    }
};

int main() {
    try {
        FileHandler fh("example.txt");
        fh.write("Hello, World!");
        // File is automatically closed when fh goes out of scope
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }
    return 0;
}