3.8. Dart Basics: Handling Exceptions

Exception handling is a crucial component of any programming language, and Dart is no exception. In Dart, exceptions are signs that something unexpected happened while the code was running. Exceptions can be caused by a number of things, such as programming errors, problems with input data, or network failures. Therefore, it's important to understand how to handle these exceptions to ensure your Flutter app continues to run smoothly.

Exception Handling in Dart

In Dart, exceptions are handled using try-catch blocks. The try block contains code that could potentially throw an exception. The catch block, on the other hand, is where you place the code that should be executed if an exception is thrown.

try {
  // code that might throw an exception
} catch (e) {
  // code to handle the exception
}

The 'e' variable in the catch block contains the exception that was thrown. You can use this variable to get more information about the exception and decide how to handle it.

In addition, Dart also supports a finally block that runs regardless of whether an exception is thrown or not. This is useful for cleaning up resources or executing code that should run regardless of whether an exception occurs.

try {
  // code that might throw an exception
} catch (e) {
  // code to handle the exception
} finally {
  // code that runs regardless of whether an exception is thrown
}

Types of Exceptions in Dart

Dart has several built-in exception classes that you can use. Some of the more common exceptions include:

• FormatException: Thrown when a string conversion operation fails.
• ArgumentError: Thrown when a function argument is invalid.
• RangeError: Thrown when a value is outside its valid range.
• NoSuchMethodError: Thrown when a nonexistent method is called.
• TypeError: Thrown when an operation encounters a value of an incompatible type.

You can also create your own exception classes in Dart. To do this, you can simply create a new class that extends the Exception or Error class.

Throwing Exceptions in Dart

In Dart, you can throw an exception using the 'throw' keyword. Here is an example:

throw FormatException('Invalid format');

This will throw a FormatException exception with the message 'Invalid format'.

In short

Exception handling is a crucial part of Dart application development. It allows you to handle unexpected situations in a controlled manner and prevent your application from crashing. By using try-catch blocks, you can catch and handle exceptions in your code. Additionally, Dart provides several built-in exception classes that you can use, and you can also create your own exception classes. Finally, you can throw exceptions in your code using the 'throw' keyword.

When developing Flutter apps, it's important to have a solid understanding of exception handling in Dart. This will allow you to create more robust and reliable applications that can handle unexpected situations effectively.

Next page of the Free Ebook:

27Dart Basics: File Manipulation

3 minutes