Exception handling in C++ technology: How to use exception classes to encapsulate exception information?

C The exception handling mechanism allows to encapsulate exception information, derive from std::exception through the exception class and use throw to throw exceptions. This class provides the what() method to obtain error messages, which can be used to handle specific exceptions in catch blocks to improve the clarity and efficiency of error handling.

Use exception class to encapsulate exception information in C

Introduction

Exception handling It is a built-in mechanism in C for handling errors and exceptions. By throwing an exception, the program can notify the caller that a problem has occurred. Exception classes allow us to encapsulate additional information about the exception, such as error code, description, or stack trace.

Syntax for using exception classes

When defining an exception class in C, it is usually derived from std::exception:

class MyException : public std::exception {
public:
    // 构造函数
    MyException(const std::string& error_message) : _error_message(error_message) {}

    // 获取错误消息
    const char* what() const noexcept override {
        return _error_message.c_str();
    }

private:
    std::string _error_message;
};

Throwing exceptions

To throw our own exceptions, we can use throw Keywords:

try {
    // 可能会抛出异常的代码
} catch(MyException& e) {
    // 处理异常
    std::cout << "异常消息：" << e.what() << std::endl;
}

Actual combat Case

Suppose we have a function that opens a file. If the file does not exist, it will throw MyException exception:

void open_file(const std::string& filename) {
    std::ifstream file(filename);
    if (!file) {
        throw MyException("文件 '" + filename + "' 不存在。");
    }
}

In the main function, we can call the open_file function and handle the potential exception:

int main() {
    try {
        open_file("example.txt");
        // 如果没有异常抛出，则继续执行
    } catch(MyException& e) {
        std::cout << "错误：" << e.what() << std::endl;
    }

    return 0;
}

Summary

By using exception classes, we can encapsulate additional information about exceptions, making error handling clearer and more efficient. Exception classes enable us to provide error details in different parts of the application and capture and handle various error conditions.

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