redux-promise-middleware-actions
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Redux action creator for making async actions with redux-promise-middleware
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# redux-promise-middleware-actions
[](https://travis-ci.org/omichelsen/redux-promise-middleware-actions)
[](https://coveralls.io/github/omichelsen/redux-promise-middleware-actions?branch=master)
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Create Redux actions with a `type` and `payload` in a standardized way. Inspired by [redux-actions](https://www.npmjs.com/package/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](https://www.npmjs.com/package/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](https://www.npmjs.com/package/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
### Synchronous action
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'
```
### Asynchronous action
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
```
### Reducer
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;
}
};
```
### Metadata
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(...) }
```
### Custome Type Delimiters
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](https://github.com/thebrodmann/deox/) for a lot of inspiration for the TypeScript types.