redux_thunk

Redux provides a simple way to update a your application's State in response to synchronous Actions. However, it lacks tools to handle asynchronous code. This is where Thunks come in.

The thunkMiddleware intercepts and calls ThunkActions, which is simply a fancy name for any function that takes 1 argument: a Redux Store. This allows you to dispatch functions (aka ThunkActions) to your Store that can perform asynchronous work, then dispatch actions using the Store after the work is complete.

The dispatched ThunkActions will be swallowed, meaning they will not go through the rest of your middleware to the Store's Reducer.

Example

// First, create a quick reducer
State reducer(String state, action) =>
    action is String ? action : state;

// Next, apply the `thunkMiddleware` to the Store
final store = new Store<String>(
  reducer,
  middleware: [thunkMiddleware],
);

// Create a `ThunkAction`, which is any function that accepts the 
// Store as it's only argument. Our function (aka ThunkAction) will
// simply send an action after 1 second.  This is just an example, 
// but  in real life, you could make a call to an HTTP service or 
// database instead!
void action(Store<String> store) async {
  final searchResults = await new Future.delayed(
    new Duration(seconds: 1),
    () => "Search Results",
  );

  store.dispatch(searchResults);
}

// You can also use a function with some parameters to create a thunk, 
// and then use it like so: store.dispatch(waitAndDispatch(3));
ThunkAction<String> waitAndDispatch(int secondsToWait) {
  return (Store<String> store) async {
    final searchResults = await new Future.delayed(
      new Duration(seconds: secondsToWait),
      () => "Search Results",
    );

    store.dispatch(searchResults);
  };
}

Credits

All the ideas in this lib are shamelessly stolen from the original redux-thunk library and simply adapted to Dart.