\((\text {Constructors Throwing Exceptions)}\) Write a program that shows a constructor passing information about constructor failure to an exception handler after a try block.

In C++, constructors are special member functions of a class that are automatically called when objects of that class are created. Under certain circumstances, a constructor might encounter a situation where it cannot properly initialize an object. In these cases, constructors have the ability to 'throw' exceptions, signaling that an error has occurred.

The process begins by defining a condition within the constructor that, if not met, triggers an exception. This is done using the 'throw' keyword, followed by an exception object. When the condition arises, the constructor throws the exception, and the object's creation is interrupted. The key is to ensure that the exception provides clear information about what went wrong, enabling developers to understand the issue at a glance. An example would be checking for invalid parameter values and throwing an exception if they do not meet the required criteria.

Using exceptions in constructors is a robust way to handle errors as it prevents the rest of the program from operating on improperly initialized objects, which can lead to undefined behavior or system crashes. The practice of throwing exceptions from constructors improves the reliability and maintainability of software applications, as it promotes explicit error handling instead of silent failures.

While C++ provides a set of standard exceptions, there are scenarios where defining custom exception classes can significantly enhance error handling. By creating a custom exception, you can tailor the error information and handling to the needs of your specific application.

To define a custom exception class, it usually inherits from the 'std::exception' class or any other appropriate standard exception class. This custom exception can include additional data members and member functions to pass along detailed information about the error condition. For instance, you might include a constructor that accepts an error message or error code and a member function to retrieve this information.

Error Message Storage

Within the custom exception class, it is common to override the 'what()' function provided by 'std::exception'. This allows your custom exception to return a specific error message when it is caught and this message is requested. The power of custom exceptions lies in their ability to convey precise, contextual information about errors, enabling developers to quickly and effectively respond to issues in their code.

The try-catch block is a fundamental component of exception handling in C++. This structure allows you to define a block of code to be tested for errors while it is being executed (the 'try' block), and a block of code to be executed when an error occurs (the 'catch' block).

In a 'try' block, you place the code that is likely to generate exceptions. If an exception does occur, the program immediately stops executing the remaining code within the 'try' block and jumps to the 'catch' block that follows. It is crucial to note that a 'catch' block should specify the exception type it is designed to handle. You can have multiple 'catch' blocks following a single 'try' block to handle different types of exceptions individually.

Handling an Exception

When the corresponding 'catch' block receives the exception, it can respond in various ways, such as logging the error, displaying a message to the user, or performing some form of recovery. In essence, the try-catch structure ensures that code execution can proceed smoothly, even if errors occur, and adroit use of this technique results in more robust and error-resistant programs.