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https://github.com/wcandillon/react-native-img-cache

Image Cache for React Native
https://github.com/wcandillon/react-native-img-cache

cache image react-native

Last synced: 13 days ago
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Image Cache for React Native

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# React Native Image Cache



[![CircleCI](https://circleci.com/gh/wcandillon/react-native-img-cache.svg?style=svg)](https://circleci.com/gh/wcandillon/react-native-img-cache)

[![npm version](https://badge.fury.io/js/react-native-img-cache.svg)](https://badge.fury.io/js/react-native-img-cache)



CachedImage component and Cache image manager for React Native.



## Deprecated



**I am no longer maintaining this library but [react-native-expo-image-cache](https://github.com/wcandillon/react-native-expo-image-cache) which depends on ExpoKit.**



**Checkout [5 things to know about Images in React Native](https://medium.com/@wcandillon/5-things-to-know-about-images-react-native-69be41d2a9ee)**



## Why do I need this?

Starting version `0.43`, the React Native [Image component](https://facebook.github.io/react-native/docs/image.html) has now a cache property: `cache: force-cache` (iOS only). This is a major improvement but only for iOS and at this time, I wasn't able to use it in a way that provides a user experience as smooth as this module.



## Installation



### rn-fetch-blob

This package has a dependency with [rn-fetch-blob](https://github.com/joltup/rn-fetch-blob).

If your project doesn't have a dependency with this package already, please refer to [their installation instructions](https://github.com/joltup/rn-fetch-blob#user-content-installation).



```bash

npm install react-native-img-cache --save

```



## Usage



### CachedImage



The `CachedImage` component assumes that the image URI will never change. The image is stored and served from the application cache. This component accepts the same properties than `Image` except for a few difference:

* `source` doesn't accept an array of image URIs like `Image` does. Please file an issue if that's something you would like to see supported.

* The `uri` property in `source` is mandatory.

* The `body` property in `source` is not supported. Please file an issue if that's something you would like to see supported.



```jsx

import {CachedImage} from "react-native-img-cache";



```



The `mutable` property implies assumes that the image URI can change over time. The lifetime of this cache is the one of the running application and it can be manually busted using `ImageCache`.



```jsx

import {CachedImage} from "react-native-img-cache";



```



### Custom Image Component



By default, the `CachedImage` component is using the [standard RN Image component](https://facebook.github.io/react-native/docs/image.html).

It is possible however to use a different component via `CustomCachedImage`. In the example below, we use the `Image` component from [react-native-image-progress](https://github.com/oblador/react-native-image-progress).



```jsx

import {CustomCachedImage} from "react-native-img-cache";



import Image from 'react-native-image-progress';

import ProgressBar from 'react-native-progress/Bar';



```



### ImageCache



#### clear()



Remove cache entries and all physical files.



```js

ImageCache.get().clear();

```



#### bust(uri)



`ImageCache` can be used to bust an image from the local cache.

This removes the cache entry but it **does not remove any physical files**.



```js

ImageCache.get().bust("https://i.ytimg.com/vi/yaqe1qesQ8c/maxresdefault.jpg");

```



#### cancel(uri)



It can also be used to cancel the download of an image. This can be very useful when [scrolling through images](https://medium.com/@wcandillon/image-pipeline-with-react-native-listview-b92d4768b17c).



```js

ImageCache.get().cancel("https://i.ytimg.com/vi/yaqe1qesQ8c/maxresdefault.jpg");

```



#### on(uri, observer, immutable)



The `ImageCache` class can register observers to the cache.



```js

const immutable = true;

const observer = (path: string) => {

    console.log(`path of the image in the cache: ${path}`);

};

ImageCache.get().on(uri, observer, immutable);

```



We use the observer pattern instead of a promise because a mutable image might have different version with different paths in the cache.



#### dispose(uri, observer)



Observers can be deregistered using `dispose`:



```js

ImageCache.get().dispose(uri, observer);

```



## Testing with jest



### Mocking CachedImage



With jest, testing a snapshot can generate errors. Jest doesn't know how to generate the component CachedImage. For fix this, you have to mock CachedImage with Image component.



```js

jest.mock('react-native-img-cache', () => {

  const mockComponent = require('react-native/jest/mockComponent')

  return {

    CustomCachedImage: mockComponent('Image'),

    CachedImage: mockComponent('Image'),

  }

})

```