Dispatching Actions

Dispatching Actions

The foundational principle of AsyncRedux: the only way to change the application state is by dispatching actions. You can dispatch from widgets (via context extensions) or from within other actions.

Five Dispatch Methods

1. dispatch()

The standard method that returns immediately. For synchronous actions, state updates before return; for async actions, the process begins and completes later.

dispatch(MyAction());

2. dispatchAndWait()

Returns a Future that completes when the action finishes and state changes, regardless of whether the action is sync or async. Returns an ActionStatus object.

var status = await dispatchAndWait(MyAction());
if (status.isCompletedOk) {
  Navigator.pop(context);
}

3. dispatchAll()

Dispatches multiple actions in parallel, returning the list of dispatched actions.

dispatchAll([BuyAction('IBM'), SellAction('TSLA')]);

4. dispatchAndWaitAll()

Dispatches actions in parallel and waits for all to complete.

await dispatchAndWaitAll([
  BuyAction('IBM'),
  SellAction('TSLA'),
]);

5. dispatchSync()

Like dispatch() but throws a StoreException if the action is asynchronous. Use when synchronous execution is mandatory.

dispatchSync(MyAction());

Dispatching from Widgets

All dispatch methods are available as BuildContext extensions:

context.dispatch(Action());
context.dispatchAll([Action1(), Action2()]);
await context.dispatchAndWait(Action());
await context.dispatchAndWaitAll([Action1(), Action2()]);
context.dispatchSync(Action());

Example button implementation:

ElevatedButton(
  onPressed: () => context.dispatch(Increment()),
  child: Text('Increment'),
)

For async dispatch in callbacks:

ElevatedButton(
  onPressed: () async {
    var status = await context.dispatchAndWait(SaveAction());
    if (status.isCompletedOk) {
      Navigator.pop(context);
    }
  },
  child: Text('Save'),
)

Dispatching from Within Actions

All dispatch methods are available inside actions via the ReduxAction base class:

class MyAction extends ReduxAction<AppState> {
  Future<AppState?> reduce() async {
    // Dispatch another action and wait for it
    await dispatchAndWait(LoadDataAction());

    // Dispatch without waiting
    dispatch(LogAction('Data loaded'));

    return state.copy(loaded: true);
  }
}

Dispatching in before() and after()

You can dispatch actions in the before() and after() lifecycle methods:

class MyAction extends ReduxAction<AppState> {
  Future<AppState?> reduce() async {
    String description = await fetchData();
    return state.copy(description: description);
  }

  void before() => dispatch(BarrierAction(true));
  void after() => dispatch(BarrierAction(false));
}

ActionStatus

The dispatchAndWait() method returns an ActionStatus object with useful properties:

var status = await dispatchAndWait(MyAction());

// Check completion state
status.isCompleted;       // Action finished executing
status.isCompletedOk;     // Completed without errors
status.isCompletedFailed; // Completed with errors

// Access error information
status.originalError;     // Error thrown by before/​reduce
status.wrappedError;      // Error after wrapError() processing

// Check method completion
status.hasFinishedMethodBefore;
status.hasFinishedMethodReduce;
status.hasFinishedMethodAfter;

You can also access status directly from the action instance:

var action = MyAction();
await dispatchAndWait(action);
print(action.status.isCompletedOk);

The notify Parameter

Dispatch methods accept an optional notify parameter (default true) that controls whether widgets rebuild on state changes:

// Dispatch without triggering widget rebuilds
dispatch(MyAction(), notify: false);

Summary Table

References

URLs from the documentation:

• https://asyncredux.com/flutter/basics/dispatching-actions
• https://asyncredux.com/flutter/basics/using-the-store-state
• https://asyncredux.com/flutter/basics/sync-actions
• https://asyncredux.com/flutter/basics/async-actions
• https://asyncredux.com/flutter/basics/store
• https://asyncredux.com/flutter/advanced-actions/redux-action
• https://asyncredux.com/flutter/advanced-actions/action-status
• https://asyncredux.com/flutter/advanced-actions/before-and-after-the-reducer
• https://asyncredux.com/flutter/testing/dispatch-wait-and-expect
• https://asyncredux.com/flutter/miscellaneous/advanced-waiting