Stop Printing Errors! Handle Them Like a Pro in Flutter

Introduction

If you've ever relied on print(error) in your Flutter production code, you're not alone. However, this approach can lead to frustration and loss of user trust. Effective error handling is crucial for maintaining a stable and reliable application. This article guides you through the evolution of error handling in Flutter, from basic printing to advanced techniques.

The Junior Stage: Printing Everything

In the early stages of development, it's common to use print(error) within try-catch blocks. While this may suffice for learning purposes, it's insufficient for real-world applications. Printing errors without context or stack traces is like shouting for help in a crowded room – no one hears you.

Common mistakes at this stage:
Spamming print(error) everywhere.
Ignoring stack traces.
Wrapping everything in try-catch without understanding the root cause.

The Mid-Level Upgrade: Debugging Like a Detective

As you gain experience, you'll transition from print to debugPrint. This is a step in the right direction, as it provides more information, including stack traces. However, relying solely on debugPrint and numerous try-catch blocks can become tedious and difficult to maintain.

try {
  fetchData();
} catch (e, stack) {
  debugPrint('Error: $e');
  debugPrintStack(stackTrace: stack);
}

The Pro Upgrade: Custom Exceptions + Global Error Catching

The professional approach involves centralizing error handling and creating custom exceptions. Flutter provides powerful tools for this, including FlutterError.onError and runZonedGuarded. These tools allow you to catch errors at the framework level and handle asynchronous errors globally.

By centralizing error handling, you can avoid scattering try-catch blocks throughout your codebase. This makes your code cleaner, more maintainable, and easier to debug.

Custom exceptions provide further organization by classifying errors into meaningful categories. This allows you to handle different types of errors in a specific and targeted manner.

class NetworkException implements Exception {
  final String message;
  NetworkException(this.message);
}

class CacheException implements Exception {
  final String message;
  CacheException(this.message);
}

void main() {
  FlutterError.onError = (details) {
    FlutterError.dumpErrorToConsole(details);
  };

  runZonedGuarded(
    () => runApp(MyApp()),
    (error, stack) {
      if (error is NetworkException) {
        debugPrint('Network issue: ${error.message}');
      } else if (error is CacheException) {
        debugPrint('Cache issue: ${error.message}');
      } else {
        debugPrint('Unhandled error: $error');
      }
    },
  );
}

Conclusion