redux-axios-middleware/README.md

# redux-axios-middleware

Redux middleware for fetching data with axios HTTP client

## Installation

```bash
npm i -S redux-axios-middleware
```

## How to use?

### Use middleware

By default you only need to import middleware from package and add it to redux middlewares and execute it with first argument being with axios instance. second optional argument are middleware options for customizing

```js
import {createStore, applyMiddleware} from 'redux';
import axios from 'axios';
import axiosMiddleware from 'redux-axios-middleware';

const client = axios.create({ //all axios can be used, shown in axios documentation
  baseURL:'http://localhost:8080/api',
  responseType: 'json'
});

let store = createStore(
  reducers, //custom reducers
  applyMiddleware(
    //all middlewares
    ...
    axiosMiddleware(client), //second parameter options can optionally contain onSuccess, onError, onComplete, successSuffix, errorSuffix
    ...
  )
)
```

### Dispatch action

Every action which have `payload.request` defined will be handled by middleware. There are two possible type definitions.

- use `action.type` with string name
- action with type will be dispatched on start, and then followed by type suffixed with underscore and
- success suffix on success, or error suffix on error

defaults: success suffix = "_SUCCESS" error suffix = "_FAIL"

```javascript
export function loadCategories() {
  return {
    type: 'LOAD',
    payload: {
      request:{
        url:'/categories'
      }
    }
  }
}
```

- use `action.types` with array of types `[REQUEST,SUCCESS,FAILURE]`
- `REQUEST` will be dispatched on start, then `SUCCESS` or `FAILURE` after request result

```javascript
export function loadCategories() {
  return {
    types: ['LOAD','AWESOME','OH_NO'],
    payload: {
      request:{
        url:'/categories'
      }
    }
  }
}
```

Actions that are handled by this middleware return a promise.  This gives you the ability to chain actions.  A good example of this might be a form.  In the form you might dispatch an actions to store the form values.  The normal flow of the action into the reducers would not be altered but you can chain a then/catch onto the initial dispatch.

```javascript
this.props.saveForm(formData)
  .then(() => {
    // router the user away
    this.context.router.push("/my/home/page")
  })
  .catch((response) => {
    //handle form errors
  })
```

Another example might be a set of actions that you want dispatched together.

```javascript
Promise.all([
  dispatch(foo()),
  dispatch(bar()),
  dispatch(bam()),
  dispatch(boom())

]).then(() => {
  dispatch(
    loginSuccess(
      token
    )
  )
})
```

### Request complete

After request complete, middleware will dispatch new action,

#### on success

```javascript
{
  type: 'AWESOME', //success type
  payload: { ... } //axios response object with data status headers etc.
  meta: {
    previousAction: { ... } //action which triggered request
  }
}
```

#### on error

Error action is same as success action with one difference, there's no key `payload`, but now there's `error`;

```js
{
    type:'OH_NO',
    error: { ... }, //axios error object with message, code, config and response fields
    meta: {
      previousAction: { ... } //action which triggered request
    }
}
```

#### if axios failed fatally, default error action with status `0` will be dispatched.

```js
{
    type:'OH_NO',
    error: {
      status: 0,
      ... //rest of axios error response object
    },
    meta: {
      previousAction: { ... } //action which triggered request
    }
}
```

### Multiple clients

If you are using more than one different APIs, you can define those clients and put them to middleware. All you have to change is import of middleware, which is passed to redux createStore function and defined those clients.

```
import { multiClientMiddleware } from 'redux-axios-middleware';
createStore(
 ...
 multiClientMiddleware(
   clients, // described below
   options // optional, this will be used for all middleware if not overriden by upper options layer
 )
)
```

`clients` object should be map of

```
{
  client: axiosInstance, // instance of axios client created by axios.create(...)
  options: {} //optional key for passing specific client options
}
```

For example:

```
{
  default: {
    client: axios.create({
       baseURL:'http://localhost:8080/api',
       responseType: 'json'
    })
  },
  googleMaps: {
    client: axios.create({
        baseURL:'https://maps.googleapis.com/maps/api',
        responseType: 'json'
    })
  }
}
```

Now in every dispatched action you can define client used:

```javascript
export function loadCategories() {
  return {
    type: 'LOAD',
    payload: {
      client: 'default', //here you can define client used
      request:{
        url:'/categories'
      }
    }
  }
}
```

If you don't define client, default value will be used. You can change default client name in middleware options.

### Middleware options

Options can be changed on multiple levels. They are merged in following direction:

```
default middleware values < middleware config < client config < action config
```

All values except interceptors are overriden, interceptors are merged in same order. Some values are changeable only on certain level (can be seen in change level column).

Legend: `M` - middleware config `C` - client config `A` - action config

key                          | type                                 | default value                                             | change level | description
---------------------------- | ------------------------------------ | --------------------------------------------------------- | ------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
successSuffix                | string                               | SUCCESS                                                   | `M` `C` `A`  | default suffix added to success action, for example `{type:"READ"}` will be `{type:"READ_SUCCESS"}`
errorSuffix                  | string                               | FAIL                                                      | `M` `C` `A`  | same as above
onSuccess                    | function                             | described above                                           | `M` `C` `A`  | function called if axios resolve with success
onError                      | function                             | described above                                           | `M` `C` `A`  | function called if axios resolve with error
onComplete                   | function                             | described above                                           | `M` `C` `A`  | function called after axios resolve
returnRejectedPromiseOnError | bool                                 | false                                                     | `M` `C` `A`  | if `true`, axios onError handler will return `Promise.reject(newAction)` instead of `newAction`
isAxiosRequest               | function                             | function check if action contain `action.payload.request` | `M`          | check if action is axios request, this is connected to `getRequestConfig`
getRequestConfig             | function                             | return content of `action.payload.request`                | `M` `C` `A`  | if `isAxiosRequest` returns true, this function get axios request config from action
getClientName                | function                             | returns `action.payload.client` OR `'default'`            | `M` `C` `A`  | attempts to resolve used client name or use defaultClientName
defaultClientName            | every possible object key type       | `'default'`                                               | `M`          | key which define client used if `getClienName` returned false value
getRequestOptions            | function                             | return `action.payload.options`                           | `M` `C`      | returns options object from action to override some values
interceptors                 | object `{request: [], response: []}` |                                                           | `M` `C`      | You can pass axios request and response interceptors. Take care, first argument of interceptor is different from default axios interceptor, first received argument is object with `getState`, `dispatch` and `action` keys

## License

This project is licensed under the MIT license, Copyright (c) 2016 Michal Svrček. For more information see `LICENSE.md`.

## Acknowledgements

[Dan Abramov](https://github.com/gaearon) for Redux [Matt Zabriskie](https://github.com/mzabriskie) for [Axios](https://github.com/mzabriskie/axios). A Promise based HTTP client for the browser and node.js