marcglasberg/asyncredux-check-internet-mixin

CheckInternet Mixin

The CheckInternet mixin verifies device connectivity before an action executes. If there's no internet connection, the action aborts and displays a dialog with the message: "There is no Internet. Please, verify your connection."

Basic Usage

class LoadText extends AppAction with CheckInternet {

  Future<AppState?> reduce() async {
    var response = await http.get('https://api.example.com/text');
    return state.copy(text: response.body);
  }
}

The mixin works by overriding the before() method. If the device lacks connectivity, it throws a UserException which triggers the standard error dialog.

Customizing the Error Message

Override connectionException() to return a custom UserException:

class LoadText extends AppAction with CheckInternet {

  @override
  UserException connectionException(UserException error) {
    return UserException('Unable to load data. Check your connection.');
  }

  Future<AppState?> reduce() async {
    var response = await http.get('https://api.example.com/text');
    return state.copy(text: response.body);
  }
}

NoDialog Modifier

Use NoDialog alongside CheckInternet to suppress the automatic error dialog. This allows you to handle connectivity failures in your widgets using isFailed() and exceptionFor():

class LoadText extends AppAction with CheckInternet, NoDialog {

  Future<AppState?> reduce() async {
    var response = await http.get('https://api.example.com/text');
    return state.copy(text: response.body);
  }
}

Then handle the error in your widget:

Widget build(BuildContext context) {
  if (context.isWaiting(LoadText)) {
    return CircularProgressIndicator();
  }

  if (context.isFailed(LoadText)) {
    var exception = context.exceptionFor(LoadText);
    return Text('Error: ${exception?.message}');
  }

  return Text(context.state.text);
}

AbortWhenNoInternet

Use AbortWhenNoInternet for silent failure when offline. The action aborts without throwing errors or displaying dialogs—as if it had never been dispatched:

class RefreshData extends AppAction with AbortWhenNoInternet {

  Future<AppState?> reduce() async {
    var response = await http.get('https://api.example.com/data');
    return state.copy(data: response.body);
  }
}

This is useful for background refreshes or non-critical operations where user notification isn't needed.

UnlimitedRetryCheckInternet

This mixin combines three capabilities: internet verification, unlimited retry with exponential backoff, and non-reentrant behavior. It's ideal for essential operations like loading startup data:

class LoadAppStartupData extends AppAction with UnlimitedRetryCheckInternet {

  Future<AppState?> reduce() async {
    var response = await http.get('https://api.example.com/startup');
    return state.copy(startupData: response.body);
  }
}

Default retry parameters:

• Initial delay: 350ms
• Multiplier: 2
• Maximum delay with internet: 5 seconds
• Maximum delay without internet: 1 second

Track retry attempts via the attempts getter and customize logging through printRetries().

Mixin Compatibility

Important compatibility rules:

• CheckInternet and AbortWhenNoInternet are incompatible with each other
• Neither CheckInternet nor AbortWhenNoInternet can be combined with UnlimitedRetryCheckInternet
• CheckInternet works well with Retry, NonReentrant, Throttle, Debounce, and optimistic mixins

Testing Internet Connectivity

Two methods for simulating connectivity in tests:

Per-action simulation - Override internetOnOffSimulation within specific actions:

class LoadText extends AppAction with CheckInternet {
  @override
  bool? get internetOnOffSimulation => false; // Simulate offline

  Future<AppState?> reduce() async {
    // ...
  }
}

Global simulation - Set forceInternetOnOffSimulation on the store:

var store = Store<AppState>(
  initialState: AppState.initialState(),
);
store.forceInternetOnOffSimulation = false; // All actions see no internet

Limitations

These mixins only detect device connectivity status. They cannot verify:

• Internet provider functionality
• Server availability
• API endpoint reachability

For server-specific connectivity checks, implement additional validation in your action's reduce() method or before() method.

References

URLs from the documentation:

• https://asyncredux.com/flutter/advanced-actions/internet-mixins
• https://asyncredux.com/flutter/advanced-actions/action-mixins
• https://asyncredux.com/flutter/advanced-actions/aborting-the-dispatch
• https://asyncredux.com/flutter/basics/failed-actions
• https://asyncredux.com/flutter/advanced-actions/errors-thrown-by-actions
• https://asyncredux.com/flutter/advanced-actions/control-mixins
• https://asyncredux.com/flutter/advanced-actions/before-and-after-the-reducer
• https://asyncredux.com/flutter/advanced-actions/redux-action
• https://asyncredux.com/flutter/basics/wait-fail-succeed
• https://asyncredux.com/flutter/testing/mocking