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runZonedGuarded in Dart Explained

Dart, Error Handling, Exception2 min read

When writing Dart code, it's essential to handle errors and exceptions properly to ensure the stability and reliability of your applications. The runZonedGuarded function is a powerful tool that allows you to catch and handle uncaught errors or exceptions within a specific zone. In this article, we will dive deep into the runZonedGuarded function and understand how it can be used effectively.

Understanding Zones

Before we explore runZonedGuarded, let's briefly discuss zones in Dart. A zone represents an execution context with its own set of error-handling mechanisms. Every Dart application has at least one zone, known as the root zone. However, you can create additional zones to isolate parts of your code.

Each zone has its own error handler, which can be customized to catch and handle uncaught errors or exceptions that occur within that specific zone. By using zones and customizing their error handlers, you can easily control how errors are handled within different parts of your application.

The runZonedGuarded Function

The runZonedGuarded function is part of the Dart core library and is used to execute a given callback function within a specified zone while protecting it with a guarded error handler. It takes two arguments:

  1. The callback function to be executed.
  2. The error handler function that will be called when an uncaught error or exception occurs within the zone.

Here's the general syntax of runZonedGuarded:

2 () {
3 // Your code here
4 },
5 (error, stackTrace) {
6 // Error handling logic here
7 },

The first argument is a callback function where you can place your code that might throw errors or exceptions. The second argument is the error handler function that will be invoked if any uncaught error or exception occurs within the zone. The error parameter receives the error or exception object, while the stackTrace parameter provides information about the stack trace at the point of the error.

Example Usage

Let's look at a simple example to understand how runZonedGuarded works in practice. Suppose we have a function that performs some complex calculations but might throw an exception. We can use runZonedGuarded to catch and handle any potential exceptions:

1void main() {
2 runZonedGuarded(
3 () {
4 performComplexCalculations(); // Potentially throws an exception
5 },
6 (error, stackTrace) {
7 print('An error occurred: $error');
8 print('Stack trace:\n$stackTrace');
9 },
10 );
13void performComplexCalculations() {
14 // Complex calculations that might throw an exception
15 throw Exception('Something went wrong!');

In this example, if the performComplexCalculations function throws an exception, it will be caught by runZonedGuarded, and the error handler function will be invoked. The error message and stack trace will then be printed to the console.

Wrapping Up

In this article, we explored the runZonedGuarded function in Dart and learned how it can be used to catch and handle uncaught errors or exceptions within a specific zone. By leveraging zones and the runZonedGuarded function, you can effectively manage error handling in your Dart applications, improving their stability and resilience.