2018-10-12 19:37:13 +00:00
|
|
|
---
|
|
|
|
title: Use Middleware to Handle Asynchronous Actions
|
|
|
|
---
|
|
|
|
## Use Middleware to Handle Asynchronous Actions
|
|
|
|
|
2018-10-23 12:30:30 +00:00
|
|
|
### Hint 1
|
|
|
|
Treat the ```dispatch``` argument as a function and pass the action events in it.
|
2018-10-12 19:37:13 +00:00
|
|
|
|
2018-10-23 12:30:30 +00:00
|
|
|
### Hint 2
|
|
|
|
The ```requestingData``` action event will be passed first.
|
2018-10-12 19:37:13 +00:00
|
|
|
|
2018-10-23 12:30:30 +00:00
|
|
|
### Hint 3
|
|
|
|
The ```receivedData``` action event will be passed after the ```setTimeout``` function.
|
|
|
|
|
|
|
|
This sequence simulates the process of requesting the data, receiving the data and then dispatching the received data.
|
|
|
|
|
|
|
|
### Hint 4
|
|
|
|
It is important that the ```data``` variable be passed as an argument of ```receivedData```.
|
|
|
|
|
|
|
|
### Solution
|
|
|
|
```javascript
|
|
|
|
const REQUESTING_DATA = 'REQUESTING_DATA'
|
|
|
|
const RECEIVED_DATA = 'RECEIVED_DATA'
|
|
|
|
|
|
|
|
const requestingData = () => { return {type: REQUESTING_DATA} }
|
|
|
|
const receivedData = (data) => { return {type: RECEIVED_DATA, users: data.users} }
|
|
|
|
|
|
|
|
const handleAsync = () => {
|
|
|
|
return function(dispatch) {
|
|
|
|
// dispatch request action here
|
|
|
|
|
|
|
|
dispatch(requestingData());
|
|
|
|
|
|
|
|
setTimeout(function() {
|
|
|
|
let data = {
|
|
|
|
users: ['Jeff', 'William', 'Alice']
|
|
|
|
}
|
|
|
|
// dispatch received data action here
|
|
|
|
|
|
|
|
dispatch(receivedData(data));
|
|
|
|
|
|
|
|
}, 2500);
|
|
|
|
}
|
|
|
|
};
|
|
|
|
|
|
|
|
const defaultState = {
|
|
|
|
fetching: false,
|
|
|
|
users: []
|
|
|
|
};
|
|
|
|
|
|
|
|
const asyncDataReducer = (state = defaultState, action) => {
|
|
|
|
switch(action.type) {
|
|
|
|
case REQUESTING_DATA:
|
|
|
|
return {
|
|
|
|
fetching: true,
|
|
|
|
users: []
|
|
|
|
}
|
|
|
|
case RECEIVED_DATA:
|
|
|
|
return {
|
|
|
|
fetching: false,
|
|
|
|
users: action.users
|
|
|
|
}
|
|
|
|
default:
|
|
|
|
return state;
|
|
|
|
}
|
|
|
|
};
|
|
|
|
|
|
|
|
const store = Redux.createStore(
|
|
|
|
asyncDataReducer,
|
|
|
|
Redux.applyMiddleware(ReduxThunk.default)
|
|
|
|
);
|
|
|
|
```
|
2018-10-12 19:37:13 +00:00
|
|
|
<!-- The article goes here, in GitHub-flavored Markdown. Feel free to add YouTube videos, images, and CodePen/JSBin embeds -->
|