Exception handling is a crucial aspect of any programming language. When executing a program, it is possible that certain errors or unexpected behavior may occur. To prevent these errors from crashing the program and causing bigger problems, we use exception handling.

Dart, the programming language developed by Google, supports exception handling. In this blog post, we will take a closer look at how to use exception handling in Dart.

What is exception? link

An exception is an event that occurs during the execution of a program and disrupts the normal flow of the program. It is typically caused by an error or unexpected behavior that the program encounters.

In simple terms, think of an exception as an indication that something has gone wrong in your program. It could be due to various reasons, such as invalid inputs, division by zero, accessing an array out of bounds, or trying to open a file that doesn’t exist.

When an exception occurs, the program may stop executing if not properly handled. However, with proper exception handling, the program can gracefully recover from the error and continue its execution.

Exception handling allows programmers to catch and handle these exceptions, providing a way to react to errors and prevent the program from crashing. It includes mechanisms to identify the type of exception, perform specific actions to handle it, and potentially recover from the error.

By using exception handling techniques, developers can create more robust and reliable software, ensuring that unexpected events or errors are handled properly rather than leading to program failures.

What is Exception Handling? link

Exception handling is the practice of identifying, catching, and handling errors or unexpected events that occur during program execution. It is a mechanism that allows a program to recover from errors and continue its execution rather than abruptly crashing.

When an error or unexpected event, known as an exception, occurs during program execution, the program can be designed to handle these exceptions gracefully. Exception handling involves detecting the occurrence of an exception, taking appropriate actions to handle it, and potentially recovering from the error.

When an error occurs, it is said that an exception has been thrown.

Dart provides a way to catch and handle exceptions using try-catch blocks.

Try-Catch Blocks link

A try-catch block is a construct that allows a programmer to attempt a certain operation and react to any exceptions that might occur. Essentially, we “try” to perform an operation. If an exception is thrown, we “catch” it and take necessary action, such as logging the error or displaying an error message.

Here is an example:

   try { 
   // perform some operation that could throw an exception
   
  } catch (e) { 
     // handle the exception
 }
  

The code inside the try block is where the operation takes place that could potentially throw an exception. The catch block is executed if an exception is thrown in the try block. The e parameter in the catch block holds information about the thrown exception.

Rethrowing Exceptions link

Sometimes you may want to handle an exception and then rethrow it. In Dart, you can rethrow an exception using the rethrow keyword.

Here is an example:

      try {  
      // perform some operation that could throw an exception
    } catch (e) { 
      
       // handle the exception  
       rethrow;
       
    }
  

The rethrow keyword rethrows the caught exception. This can be helpful in cases where you need to handle an exception at one level of the program and let higher-level code handle the same exception.

On Clause link

In addition to try and catch, Dart also supports an on clause for catching specific exceptions.

Here is an example:

  try {  

  // perform some operation that could throw a FormatException 

} on FormatException catch (e) { 
  
   // handle the exception
   
   }
  

In this example, the catch block will only execute if a FormatException is thrown. The e parameter in the catch block contains information about the thrown exception.

Finally Block link

Finally, Dart also has a finally block that executes regardless of whether or not an exception is thrown.

Here is an example:

   try { 

   // perform some operation that could throw an exception

   } catch (e) {  

    // handle the exception 

    } finally {  

      // code to execute regardless of whether or not an exception is thrown

       }
  

In this example, the code in the finally block will execute whether or not an exception is thrown in the try block. This can be helpful for releasing resources or closing files that were opened in the try block.

Summary link

• Exception handling in Dart is a crucial part of programming as it allows programmers to catch and handle errors or unexpected events that may occur during program execution.

• Exception handling helps in preventing program crashes by providing a way to gracefully recover from errors and continue program execution.

• Dart uses try-catch blocks to catch and handle exceptions. The code inside the try block is where the potentially problematic operation takes place, while the catch block is executed if an exception is thrown in the try block.

• Exception rethrowing is possible in Dart using the rethrow keyword, which allows for handling exceptions at one level and passing them to higher-level code for further handling.

• Dart also supports the use of the on clause and finally block. The on clause is used to catch specific exceptions, while the finally block contains code that is executed regardless of whether an exception is thrown or not.