redux-promise-middleware-actions


Create Redux actions with a type and payload in a standardized way. Inspired by redux-actions but simpler and with special support for asynchronous actions (promises).

Has no dependencies and is tiny (~680 bytes gzipped). First class TypeScript support.

Works with redux-promise-middleware to handle asynchronous actions by dispatching pending, fulfilled and rejected events based on the state of the input promise.

Goals of this library:

* Reference action creators directly - no need to maintain an action type enum/list
* Automatically generate actions for pending, fulfilled and rejected outcomes of a promise payload
* Have statically typed access to all action types - no need to manually add a type suffix like "_PENDING"
* TypeScript support so asynchronous actions can't be confused for normal synchronous actions

Note: If you are using TypeScript this library requires TypeScript 3. For TypeScript 2 use version 1 of this library.

Installation

You need to install this library as well as redux-promise-middleware.

``
npm install redux-promise-middleware-actions redux-promise-middleware
`

Include redux-promise-middleware when you create your store:

`js
import promiseMiddleware from 'redux-promise-middleware';

composeStoreWithMiddleware = applyMiddleware(
promiseMiddleware,
)(createStore);
`
NOTE: This library is not yet compatible with the promiseTypeSuffixes option of redux-promise-middleware

Usage

$3

Synchronous actions works exactly like redux-actions. You supply a function that returns whatever payload the action should have (if any).

`js
import { createAction } from 'redux-promise-middleware-actions';

export const foo = createAction('FOO', (num) => num);

dispatch(foo(5)); // { type: 'FOO', payload: 5 }
`

When handling the action in a reducer, you simply cast the action function to a string to return the type. This ensures type safety (no spelling errors) and you can use code navigation to find all uses of an action.

`js
const fooType = foo.toString(); // 'FOO'
`

$3

When you create an asynchronous action you need to return a promise payload. If your action is called FOO the following events will be dispatched:

1. FOO_PENDING is dispatched immediately
2. FOO_FULFILLED is dispatched when the promise is resolved
* ... or FOO_REJECTED is dispatched instead if the promise is rejected

`js
import { createAsyncAction } from 'redux-promise-middleware-actions';

export const fetchData = createAsyncAction('FETCH_DATA', async () => {
const res = await fetch(...);
return res.json();
});

dispatch(fetchData()); // { type: 'FETCH_DATA_PENDING' }
`

An async action function has three properties to access the possible outcome actions: pending, fulfilled and rejected. You can dispatch them directly (in tests etc.):

`js
dispatch(fetchData.pending()); // { type: 'FETCH_DATA_PENDING' }
dispacth(fetchData.fulfilled(payload)); // { type: 'FETCH_DATA_FULFILLED', payload: ... }
dispacth(fetchData.rejected(err)); // { type: 'FETCH_DATA_REJECTED', payload: err, error: true }
`

But normally you only need them when you are writing reducers:

`js
case fetchData.pending.toString(): // 'FETCH_DATA_PENDING'
case fetchData.fulfilled.toString(): // 'FETCH_DATA_FULFILLED'
case fetchData.rejected.toString(): // 'FETCH_DATA_REJECTED'
`

Note that if you try and use the base function in a reducer, an error will be thrown to ensure you are not listening for an action that will never happen:

`js
case fetchData.toString(): // throws an error
`

$3

To create a type safe reducer, createReducer takes a list of handlers that accept one or more actions and returns the new state. You can use it with both synchronous and asynchronous action creators.

#### createReducer(defaultState, handlerMapsCreator)

`js
import { createAsyncAction, createReducer } from 'redux-promise-middleware-actions';

const fetchData = createAsyncAction('GET', () => fetch(...));

const defaultState = {};

const reducer = createReducer(defaultState, (handleAction) => [
handleAction(fetchData.pending, (state) => ({ ...state, pending: true })),
handleAction(fetchData.fulfilled, (state, { payload }) => ({ ...state, pending: false, data: payload })),
handleAction(fetchData.rejected, (state, { payload }) => ({ ...state, pending: false, error: payload })),
]);

reducer(undefined, fetchData()); // { pending: true, data: ..., error: ... }
`

#### asyncReducer(asyncActionCreator)

It can get tedious writing the same reducer for every single async action so we've included a simple reducer that does the same as the example above:

`js
import { asyncReducer } from 'redux-promise-middleware-actions';

const fetchData = createAsyncAction('GET', () => fetch(...));
const fetchReducer = asyncReducer(fetchData);

fetchReducer() // { data?: Payload, error?: Error, pending?: boolean }
`

You can also combine it with an existing reducer:

`js
export default (state, action) => {
const newState = fetchReducer(state, action);

switch (action.type) {
case 'SOME_OTHER_ACTION':
return { ... };
default:
return newState;
}
};
`

$3

You can add metadata to any action by supplying an additional metadata creator function. The metadata creator will receive the same arguments as the payload creator:

#### createAction(type, payloadCreator, metadataCreator)

`js
const foo = createAction(
'FOO',
(num) => num,
(num) => num + num
);

dispatch(foo(5)); // { type: 'FOO', meta: 10, payload: 5 }
`

#### createAsyncAction(type, payloadCreator, metadataCreator)

`js
const fetchData = createAsyncAction(
'FETCH_DATA',
(n: number) => fetch(...),
(n: number) => ({ n })
);

dispatch(fetchData(42));
// { type: 'FETCH_DATA_PENDING', meta: { n: 42 } }
// { type: 'FETCH_DATA_FULFILLED', meta: { n: 42 }, payload: Promise<...> }
// { type: 'FETCH_DATA_REJECTED', meta: { n: 42 }, payload: Error(...) }
`

$3

You can specify a different type delimiter for your async actions:

#### createAsyncAction(type, payloadCreator, metadataCreator, options)

`js
const foo = createAsyncAction(
'FETCH_DATA',
(n: number) => fetch(num),
undefined,
{ promiseTypeDelimiter: '/' }
);

dispatch(foo());
// { type: 'FETCH_DATA/PENDING' }
// { type: 'FETCH_DATA/FULFILLED', payload: ... }
// { type: 'FETCH_DATA/REJECTED', payload: ... }
``

Acknowledgements

Thanks to Deox for a lot of inspiration for the TypeScript types.