Handful of utilities you should keep in your toolbelt to handle offline/online connectivity in React Native. It supports both iOS and Android platforms. You can leverage all the functionalities provided or just the ones that suits your needs, the modules are conveniently decoupled.
Check out this medium article to see the power of the library with real world examples! 🚀
When you are building your React Native app, you have to expect that some users may use your application in offline mode, for instance when travelling on a Plane (airplane mode) or the underground (no signal). How does your app behaves in that situation? Does it show an infinite loader? Can the user still use it seamlessly?
Having an offline first class citizen app is very important for a successful user experience. React Native ships with NetInfo module in order to detect internet connectivity. The API is pretty basic and it may be sufficient for small apps but its usage gets cumbersome as your app grows. Besides that, it only detects network connectivity and does not garantee internet access so it can provide false positives.
This library aims to gather a variety of modules that follow React and redux best practises, in order to make your life easier when it comes to deal with internet connectivity in your React Native application.
- Offline/online conditional rendering through HOC or Render Callback techniques
- Reducer to keep your connectivity state in the Redux store
- Redux middleware to intercept internet request actions in offline mode and apply DRY principle
- Compatibility with async middleware libraries like redux-thunk, redux-saga and redux-observable
- A step further than
NetInfodetecting internet access besides network connectivity - Offline queue support to automatically re-dispatch actions when connection is back online or dismiss actions based on other actions dispatched (i.e navigation related)
- Typed with Flow
$ yarn add react-native-offline
This library uses NetInfo module from React Native underneath the hood. To request network info in Android an extra step is required, so you should add the following line to your app's AndroidManifest.xml as well:
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
In order to render stuff conditionally with ease. They internally listen to connection changes and also provide an extra layer of reliability by ensuring there is internet access when reporting online. For that, a HEAD request is made to a remote server.
Higher order function that returns a higher order component (HOC).
withNetworkConnectivity(config: Config): (WrappedComponent) => EnhancedComponent
type Config = {
withRedux?: boolean = false,
timeout?: number = 3000,
pingServerUrl?: string = 'https://google.com'
}withRedux: flag that indicates whether the HoC should be wired up to the redux store. By default, this parameter is false and the HoC injects isConnected as a prop into WrappedComponent. If true provided, it won't act as a component utility and pass any prop down, but instead perform the needed actions to sync up with the store. See below Redux integration for more details.
timeout: amount of time (in ms) that the component should wait for the ping response. Defaults to 3s.
pingServerUrl: remote server to ping to. It defaults to https://google.com since it's probably one the most stable servers out there, but you can provide your own if needed.
import React from 'react';
import { Text } from 'react-native';
import { withNetworkConnectivity } from 'react-native-offline';
const YourComponent = ({ isConnected }) => (
<Text>{isConnected ? 'Look ma, I am connected to the internet!' : 'Offline :('}</Text>
);
export default withNetworkConnectivity()(YourComponent);React component that accepts a function as children. It allows you to decouple your parent component and your child component, managing connectivity state on behalf of the components it is composed with, without making demands on how that state is leveraged by its children. Useful for conditionally render different children based on connectivity status. timeout and pingServerUrl can be provided through props in this case.
type Props = {
children: (isConnected: boolean) => React$Element<any>
timeout?: number,
pingServerUrl?: string
}...
import { ConnectivityRenderer } from 'react-native-offline';
const YourComponent = () => (
<View>
<Text>Image Screen</Text>
<ConnectivityRenderer>
{isConnected => (
isConnected ? (
<Button title="Download image" />
) : (
<Text>Downloading images is disabled since you are offline</Text>
)
)}
</ConnectivityRenderer>
<View>
<Text>Another Section</Text>
</View>
<ConnectivityRenderer>
{isConnected => (
<SnackBar
message="You are currently offline"
showIf={!isConnected}
duration={3000}
/>
)}
</ConnectivityRenderer>
</View>
);Note: since this component will re-render its children every time its parent's props or state changes, it's recommended to use it on leaf components in your tree.
There are 3 features that this library provides in order to leverage offline capabilities in your redux store: a reducer, a middleware and an offline queue system. You can use all of them or just the ones that suits your needs.
A network reducer to be provided to the store.
type NetworkState = {
isConnected: boolean,
actionQueue: Array<*>
}// configureStore.js
import { createStore, combineReducers } from 'redux'
import { reducer as network } from 'react-native-offline';
const rootReducer = combineReducers({
// ... your other reducers here ...
network,
});
const store = createStore(rootReducer);
export default store;2.- Wrap your top most React component into withNetworkConnectivity and configure it with withRedux = true.
The other config parameters, timeout and pingServerUrl can be provided to the store as well. Make sure your component is a descendant of the react-redux <Provider> component, so that withNetworkConnectivity has access to the store.
// Root.js
import store from './configureStore';
import React from 'react';
import { Provider } from 'react-redux';
import { withNetworkConnectivity } from 'react-native-offline';
let App = () => (
<Navigator>
<MainScreen />
<OtherScreen />
</Navigator>
);
App = withNetworkConnectivity({
withRedux: true // It won't inject isConnected as a prop in this case
})(App);
const Root = () => (
<Provider store={store}>
<App />
</Provider
);Now your network state can be accessed by any Redux container inside mapStateToProps(), as state.network.isConnected.
Note: If you wanna listen to the action dispatched internally in your reducers, import the offline action types and reference CONNECTION_CHANGE:
import { offlineActionTypes } from 'react-native-offline';
...
if(action.type === offlineActionTypes.CONNECTION_CHANGE) // do something in your reducer
...Function that returns a redux middleware which listens to specific actions targetting API calls in online/offline mode.
createNetworkMiddleware(config: Config): ReduxMiddleware
type Config = {
regexActionType?: RegExp = /FETCH.*REQUEST/,
actionTypes?: Array<string> = []
}This is the setup you need to put in place for libraries such as redux-saga or redux-observable, which rely on plain actions being dispatched to trigger async flow:
regexActionType: regular expression to indicate the action types to be intercepted in offline mode.
By default it's configured to intercept actions for fetching data following the Redux convention. That means that it will intercept actions with types such as FETCH_USER_ID_REQUEST, FETCH_PRODUCTS_REQUEST etc.
actionTypes: array with additional action types to intercept that don't fulfil the RegExp criteria. For instance, it's useful for actions that carry along refreshing data, such as REFRESH_LIST.
For redux-thunk library, the async flow is wrapped inside functions that will be lazily evaluated when dispatched, so our store is able to dispatch functions as well. Therefore, the configuration differs:
- Make sure to use a named function instead of an anonymous arrow function for the thunk returned by your action creator.
- Use
interceptInOfflineproperty in your thunk and set it totrue.
Example:
export const fetchUser = (url) => {
function thunk(dispatch) {
fetch(url)
.then((response) => response.json())
.then((responseJson) => {
dispatch({type: FETCH_USER_SUCCESS, payload: responseJson});
})
.catch((error) => {
console.error(error);
});
};
thunk.interceptInOffline = true; // This is the important part
return thunk; // Return it afterwards
};You should apply the middleware to the store using applyMiddleware. The network middleware should be the first on the chain, before any other middleware used for handling async actions, such as redux-thunk, redux-saga or redux-observable.
import { createStore, applyMiddleware } from 'redux';
import { createNetworkMiddleware } from 'react-native-offline';
import createSagaMiddleware from 'redux-saga';
const sagaMiddleware = createSagaMiddleware();
const networkMiddleware = createNetworkMiddleware();
const store = createStore(
rootReducer,
applyMiddleware([networkMiddleware, sagaMiddleware])
);When you attempt to fetch data on the internet by means of dispatching a plain action or a thunk in offline mode, the middleware blocks the action and dispatches an action of type @@network-connectivity/FETCH_OFFLINE_MODE instead, containing useful information about "what you attempted to do". The action dispatched signature for plain objects is as follows:
type FetchOfflineModeActionForPO = {
type: '@@network-connectivity/FETCH_OFFLINE_MODE',
payload: {
prevAction: {
type: string, // Your previous action type
payload?: any, // Your previous payload
}
}
}And for thunks it attaches it under prevThunk property:
type FetchOfflineModeActionForThunks = {
type: '@@network-connectivity/FETCH_OFFLINE_MODE',
payload: {
prevThunk: Function
}
}That allows you to react conveniently and update your state in the way you desire, based on your previous intent. Just reference FETCH_OFFLINE_MODE action type in your reducer:
import { offlineActionTypes } from 'react-native-offline';
...
if(action.type === offlineActionTypes.FETCH_OFFLINE_MODE) // do something in your reducer
...SnackBars, Dialog, Popups, or simple informative text are good means of conveying to the user that the operation failed due to lack of internet connection.
A queue system to store actions that failed due to lack of connectivity. It works for both plain object actions and thunks. It allows you to:
- Re-dispatch the action/thunk as soon as the internet connection is back online again
- Dismiss the action from the queue based on a different action dispatched (i.e. navigating to a different screen, the fetch action is no longer relevant)
In order to configure your PO actions to interact with the offline queue you need to use the meta property in your actions, following flux standard actions convention. They need to adhere to the below API:
type ActionToBeQueued = {
type: string,
payload?: any,
meta: {
retry?: boolean, // By passing true, your action will be enqueued on offline mode
dismiss?: Array<string> // Array of actions which, once dispatched, will trigger a dismissal from the queue
}
}- Action that will be added to the queue on offline mode and that will be re-dispatched as soon as the connection is back online again
const action = {
type: 'FETCH_USER_ID',
payload: {
id: 2
},
meta: {
retry: true
}
};- Action that will be added to the queue on offline mode and that will be re-dispatched as soon as the connection is back online again, as long as a
NAVIGATE_BACKaction type hasn't been dispatched in between, in which case the action would be removed from the queue.
const action = {
type: 'FETCH_USER_ID',
payload: {
id: 2
},
meta: {
retry: true,
dismiss: ['NAVIGATE_BACK']
}
};- For thunks, append
interceptInOfflineandmetaproperties to the function returned by the action creator, wheremetahas the same shape as for Flux actions:
function fetchData(dispatch, getState) {
dispatch({ type: FETCH_USER_ID_REQUEST, payload: { id: '3' } });
...
}
fetchData.interceptInOffline = true; // In order to be intercepted by the middleware
fetchData.meta = {
retry?: boolean, // By passing true, your thunk will be enqueued on offline mode
dismiss?: Array<string> // Array of actions which, once dispatched, will trigger a dismissal from the queue
}Thanks to Spencer Carli for his awesome article about Handling Offline actions in React Native, which served me as inspiration for the offline queue implementation.
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