Gain insights into Dart's object-oriented features, explore extensions, enums, mixins, and asynchronous programming. Discover hands-on code practice to confidently apply Dart in your projects.

dart.tar.gz

dart2_7

Dart is a fully object-oriented, class-based, simple, and clean language. Google’s popular mobile framework, Flutter uses Dart language to implement high-quality native applications, so it’s recommended that you understand Flutter before beginning this course.

In this course, you will dive deep into Dart 2 language features while using interactive hands-on code playgrounds. This course will help you become confident with Dart extensions, enums, mixins, generics, libraries, asynchronous programming, class variables, callable classes, and generator functions.

By the end of this course, you will have a strong understanding of Dart principles, and you’ll be ready to start using this powerful language in your own projects.

Developing Web Applications with Dart

# Handling Errors in Streams

When an error(s) occurs, a Stream can notify it as an error event similar to a data event. The stream can notify about an error in one of three ways:

* Stream notifies the first error event and stops. We will see a few examples of this case in the lesson.
* Stream notifies multiple error events.
* Stream notifies error event(s) and continue delivering events.

## Error handling in `await for` block

An error event can be responded to within the `try/catch` block. Let's see the first option to handle one error event by putting an `await for` loop in the previous example inside the `try/catch` block. 

To be able to see the `catch` block respond to the error event, we need to tweak `createStream` to throw an `Exception` at some point. Let's assume the error event occurs when accessing the 5th number.

```dart
//Generated Stream with numbers. Added exception on purpose for demonstration
Stream<int> createNumberStreamWithException(int last) async* {
  for (int i = 1; i <= last; i++) {
    if (i == 5) {
      throw new Exception("Demo exception when accessing 5th number");
    }
    yield i; //to be able to send spaced out events
  }
}
```

The `handlingExceptionUsingAwaitFor()` is executed in the `main()` method.

In this lesson, you will learn to handle errors in Streams.

Introduction

Dart Extensions

Dart Enums

Dart Mixins

Dart Generics

Dart Libraries

Asynchronous Programming In Dart

Miscellaneous

Next Steps

Streams #3

Handling Errors in Streams