| name | asyncredux-check-internet-mixin |
| description | Add the CheckInternet mixin to ensure network connectivity before action execution. Covers automatic error dialogs, combining with NoDialog for custom UI handling, and AbortWhenNoInternet for silent abort. |
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:
